We still have a source, although I don't know how much longer it will be available. Here, possession of an explosive is illegal, don't know about making it?
Even though BP is classified as class 1 Explosive here, it is legal to possess it.
I've got enough for a while, but getting expensive- $40.00 per pound. For my .69, that's less that's only 73 shots per pound on the trail or plinking at close range.