but I understand that many local/smaller feed stores throughout the US carry it if you wanted to save shipping charges. It might
just be a matter of looking in your local phone book for feed stores and calling around a bit to see who carries it and has it in stock.
I have heard people talk here at BYC about Perma Guard as being the brand they preferred.
I get mine from eBay. Also, you just sprinkle the DE around the coop, nest boxes, etc. You won't use it solely for dust bathing. You or your chickens don't want to breathe it in.