I got it at a specialist reptile store, and then it became popular and was started to get onto the shelves at Pets At Home stores (biggest pet retailer). I just did some research because you're in the United States, I don't think it's all too well known in the States, it's probably going to be too impractical for you to ship the stuff from Amazon every time, too.

You might be able to find out from someone here if it's available in the States. If not, just go for what's more practical.