Can someone tell me how much it costs to hire a lawyer to write up a commission business contract?

I'm the middleman for a transaction between the buyer and seller. I collect commission from the seller and i want to make sure they pay me as agreed verbally so it should be an enforceable contract.

I also need to the contract to include:-
Non-disclosure about the commission
Exclusivity as the only agent for the product for a specific period of time
No liability for any damanges of the products etc
Legal action falls under my jurisdiction
That any parties introduced through me whether they buy through them or not, will incur commission.
And any other clause that the lawyer should recommend me to include.

May i know how much this would cost? Any lawyer here? Or law firm website to recommend?

Appreciate any help at all.