Well, I checked with my local meat market (Mpls area) who also handles the standard seafood. This in response to a remark made by my brother-in-law (who is in the wholesale herring biz) that all of the markets used the same wholesaler. I had the guy at the market give them a call, and they affirmed they did handle it, fresh frozen, in 5 pound blocks. He said he would buy a block if I would buy a couple of pounds. I told him I would let him know when I returned from Puerto Rico. I was in there yesterday to pick up a roast and spotted conch meat in vacuum packed freezer bags, still frozen, so I grabbed one (about a pound and a half, just the good meat, 10.99 a pound). I do have a recipe, and my wifes recollection of what the Hustler boat guy used to make some of the best ceviche I have ever tasted, so I am going to be experimenting this week.
My suggestion, check with your local meat market. If no go there, shoot me an e-mail (email@example.com) and I will get you hooked up.