Yeah, my feeling is that they stopped making the old ones because truthfully, they just contain flash powder, which can be used for "other things". The new ones I suspect, can't. FP ingredients are VERY controlled nowadays, and can't be shipped normally W/O added hassle and expense.
W.O.C., they're tons of fun, and they do make them that are 22LR and up sensitive, and you can buy them on the internet. I was looking at them yesterday.