I usually buy at a couple of privately-owned "health food" stores here in Oklahoma City--the Health Food Center and the General Nutrition Center. HFC carries a pretty impressive variety (and they are expanding their store), so they might be a good outlet for your product.
I've also bought at a MaxMuscle store in OKC because it's operated by fellow strength/bodybuilding aficionados, although their prices, though discounted, aren't quite as low as HFC's.