I had some 10 years ago and unfortunately lost them when I had my heart attack- it has taken me 9 years to find some more, I tried ordering via wholesalers but they just never came in. Then I got lucky, a member on a UK forum I'm on mentioned he had seen them advertised at a LFS on FB. I phoned the shop he still had them and I bought all 9. It turned out they came in as a 'box filler' on an Australian import. I don't know about in the US but they just don't come into the UK very often.
Just to make you jealous here's a video of them spawning