Form of Subscription Agreement between the Registrant and the insiders for Private Units

Exhibit 10.5

Orisun Acquisition Corp.

555 Madison Avenue, Room 543

New York, NY 10022

Ladies and Gentlemen:

Orisun Acquisition Corp. (the “Company”), a blank check company formed for the purpose of acquiring one or more businesses or entities (a “Business Combination”), intends to register its securities under the Securities Act of 1933, as amended (“Securities Act”), in connection with its initial public offering (“IPO”), pursuant to a registration statement on Form S-1 (“Registration Statement”).

The undersigned hereby commits that it will purchase 200,000 units of the Company (“Private Units”), each Private Unit consisting of one share of common stock of the Company, par value $0.00001 per share (the “Common Stock”), one warrant entitling its holder to purchase one-half of one share of Common Stock (each a “Warrant”), and one right to receive one-tenth (1/10) of a share of Common Stock (each a “Right”), at $10.00 per Private Unit, for a purchase price of $2,000,000 (the “Private Unit Purchase Price”).

The undersigned hereby agrees that it will purchase an additional amount of units of the Company (“Over-Allotment Units”), up to a maximum of 15,000 Over-Allotment Units, or a maximum purchase price of $150,000 (“Over-Allotment Unit Purchase Price”, together with the Private Unit Purchase Price, the “Purchase Price”), in the event Chardan Capital Markets, LLC (“Chardan”) exercises its over-allotment option, such that the amount held in the trust account (as described in the Registration Statement) does not fall below $10.00 per share for each share of Common Stock sold in the IPO.

At least twenty-four (24) hours prior to the effective date of the Registration Statement, the undersigned will cause the Private Unit Purchase Price to be delivered to Loeb & Loeb LLP (“Loeb”), counsel for the Company, by wire transfer as set forth in the instructions attached as Exhibit A to hold in a non-interest bearing account until the Company consummates the IPO.

The consummation of the purchase and issuance of the Private Units shall occur simultaneously with the consummation of the IPO and the consummation of the purchase and issuance of the Over-Allotment Units shall occur simultaneously with the closing of any exercise of the over-allotment option related to the IPO. Simultaneously with the consummation of the IPO, Loeb shall deposit the Private Unit Purchase Price, without interest or deduction, into the trust fund (“Trust Fund”) established by the Company for the benefit of the Company’s public stockholders as described in the Registration Statement. If the Company does not complete the IPO within ten (10) days from the date of this letter, the Purchase Price (without interest or deduction) will be returned to the undersigned.

Each of the Company, and the undersigned acknowledges and agrees that Loeb is serving hereunder solely as a convenience to the parties to facilitate the purchase of the Private Units and Loeb’s sole obligation under this letter agreement is to act with respect to holding and disbursing the Purchase Price for the Private Units as described above. Loeb shall not be liable to the Company, Chardan or the undersigned, or any other person or entity in respect of any act or failure to act hereunder or otherwise in connection with performing its services hereunder unless Loeb has acted in a manner constituting gross negligence or willful misconduct. The Company and the undersigned shall indemnify Loeb against any claim made against it (including reasonable attorney’s fees) by reason of it acting or failing to act in connection with this letter agreement except as a result of its gross negligence or willful misconduct. Loeb may rely and shall be protected in acting or refraining from acting upon any written notice, instruction or request furnished to it hereunder and believed by it to be genuine and to have been signed or presented by the proper party or parties.

The Private Units and Over-Allotment Units will be identical to the units to be sold by the Company in the IPO. Additionally, the undersigned agrees:

The undersigned acknowledges and agrees that the purchaser of the Private Units and Over-Allotment Units will execute agreements in form and substance typical for transactions of this nature necessary to effectuate the foregoing agreements and obligations prior to the consummation of the IPO as are reasonably acceptable to the undersigned, including but not limited to an insider letter.

The undersigned hereby represents and warrants that:

With respect to the Private Units purchased by Chardan or any other member of FINRA, the holder of such Private Units agrees that, in accordance with FINRA Rule 5110(g)(1), it will not sell, transfer, assign, pledge or hypothecate in whole or in part any Private Units, shares of Common Stock, warrants, and rights underlying the Private Units, or shares of Common Stock that are issuable pursuant to the warrants or rights included in the Private Units (in whole or in part) or any interest herein, or subject any such securities to any hedging, short sale, derivative or put or call transaction that would result in the economic disposition of such securities, for a lock-up period of 180 days following the effective date of the Registration Statement or the commencement of sales in the IPO to anyone other than (i) an underwriter or a selected dealer participating in the IPO or (ii) any successor, officer or partner of Chardan or of any such underwriter, selected dealer or successor. Additionally, certain registration rights have been provided with respect to the Private Units purchased by Chardan and other holders, which registration rights will at all times be in compliance with FINRA Rule 5110(f)(2)(G)(iii)-(v).

This letter agreement constitutes the entire agreement between the undersigned and the Company with respect to the purchase of the Private Units and Over-Allotment Units, and supersedes all prior and contemporaneous understandings, agreements, representations and warranties, both written and oral, with respect to the same.

Signature Page to the Subscription Agreement

Exhibit A

Wire Instructions

Bank Name: Citigroup Private Bank

Bank Address: 153 East 53rd Street, New York, NY 10022

Account Name: Loeb & Loeb LLP - Trust Account

Account Number: 24576266

Routing/ABA Number (Domestic Wires): 021000089

Swift Code (Foreign Wire): CITIUS33

Reference: Orisun 232137-10001

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