All of the above is good advice. To amplify, the level of interest would depend upon quality, delivery and price, probably in that order. Aluminum gears are harder to find than aluminum sprockets.
Quality: Junk gears are, well, junk. People will pay a little more for good quality.
Delivery: This might be first. FIRST teams spend a huge amount of money with McMaster-Carr, because you can order it today and have it tomorrow, almost anything in their huge catalog. Having it tomorrow easily justifies a 30% price premium (in certain cases) for me.
Price: Least important, unless there is someone with as good of a product, with similar delivery, at a lower cost - I'm thinking AndyMark for sprockets here.
So, how does a potential supplier reach all (or most) FIRST teams? You can advertise on ChiefDelphi. You can look up every team on USFIRST.org, determine a mailing address, and send a bulk mail flyer/letter/brochure out.
You can hijack the NASA Kickoff feed... er, scratch that, bad idea.
Don