Well I guess I have to agree with Rob, buy it while you can and stockpile it.
That said, I started experimenting with making BP last yr.
Started with hardware store bought items , wood charcoal, stump remover and garden sulfur. IT SUCKED.
Bought potassium, sulfur from skylighter and made my our red fir charcoal and BOOM, it worked.
Now to be fair, I haven't tested it in a gun yet, still in mill powder form. Planning on buying a press once my new shop is built. Then corning it.
It is an easy process , no wet mixing of ingredients , all done dry, separately in a harbor freight 6# tumbler in an outbuildings, don't do it in your kitchen. Then mixed in small mounts .
Good luck. Be careful , have fun
Kevin