My instructor orders my stuff for me through some vendor he has a account with, and never thought much about being sponsored to compete so I can't comment on that.
This is an interesting topic. I'll need to look into sponsorships for bjj tournament competitors a bit more to see how that process compares to finding sponsors for MMA. I recently wrote an article for MMApipeline.com that discusses how to go about getting sponsored for guys just starting out in MMA. Most of that info should work for bjj competitors as well. The article can be found here:
best of luck!