It's not just a case of finding a wholesaler, it's getting approved.

Wholesalers don't want to get caught undercutting their customers. Consequently, they want you to look like a professional business before they will sell to you. A yellow pages ad is a common requirement that they can easily check. Photos of the business are also sometimes required. If you have a professionally lettered truck, I'd think that would be a big boost.

I do a little bike repair out of my home. I buy most of the parts that I need through a local LBS which gives me a substantial discount.