I've bought them from aquraium village, pets warehouse, fish town, ect. They prob all get them from the same breeder. Im not sure if the guy I got them from last time sells to the public but has 3 different sizes, Small med large but i got them mixed. The small ones clown fish and wrasse can eat in a bite or 2, the large they don't seem to go after. The medium they get in 2 bites while puffers and triggers get in 1 and the little guy's follow and clean up whatever parts they miss.
A trick with these for fussy eaters is to feed the shrimp whatever you want your fish to eat...flakes, spirulina, pellets, ect and my fish developed a taste for it. I used to feed them flakes and now certain fish that wouldent eat flakes do now. No idea if its coincidence or not