I bought it last year at Advance/Discount auto parts. It isn't on display, you have to ask for it. And when I asked for it, the kid behind the parts counter looked at me like I was from Mars - he honestly didn't know what the stuff was. Fortunately, the store manager was within earshot and he said "We keep it locked up in my office." You will have to show a 609 certification, which costs $15 and is trivially easy to get at
IMACA.