hi.
I never heard of anyone who sells them. The problem is that they almost always live in an Acrop, and no one want to catch them and leave the host coral alone. They are ususally "free" in wild caught Acrop. if you buy the coral you know....
You can always lie and tell other people that they are harmfully pests, and suggest to catch and ship them to you for "proper" disposal.
Ditto Righty's request. I'm grappling with that concern with stocking my new tank. I would like nothing more than to be able to say every cnardian in there was captive raised, but... then I'll never get an Acro crab. Seems like an insignificant thing to throw the whole CR plan out the window on, but I have to admit, it's giving me pause for thought. You can get Anemone crabs and shrimp outside of buying an anemone, but I've never seen acro crabs for sale outside of a head.