georgiacrickets.com I think they're part of a franchise, so wherever you are, there's one of that group near you. They tell you the exact size when you order. They also have special built tubs and send you calcium, cricket deodorizer, food (not gut-load), and cricket water with the tub when you order. The tubs have sanded sides to maximize the space so they don't cannibalize. If you're like, "hey, I'll switch to roaches" or "hey, I think I'll try a strange new worm or something." They have it. They also have feeder packages for variety.
Size: Personally, I ordered large 3 times in a row and probably half of them died, no matter how many I ordered. They just don't live long enough. I order medium crickets and feed him more.
PetCo had me paying more to feed 1 veiled chameleon than my 2 dogs and 2 guinea pigs combined. I know it makes me a jerk, but when I see people in PetCo buying crickets, I tell them about his place as soon as the employee walks away.