Can you still by the original black powder?

Yes but few stores carry it any more due to the storage restrictions; You have to order it by the 25 pound case. Unless you find a place that sells it; none around here.
Several places sell it mail order.

Grafs carries it. You don't have to order it (from them) in a 25 pound case.

Powder Valley

https://www.powdervalleyinc.co...tags=1&sku=1&ixwps=1

This is perfect example why it is good to have ones location posted, even if they leave it at the "state" level.
It is a long way from east coast to west coast and from border to border, heck they claim that it is 535 miles from Memphis to Trade (TN).

Folks can offer the best information if they have some idea where they talking about geographically.

A bunch of restrictions on storage for dealers and so few are interested in selling it. Some more stringent "local" conditions may well prevail also.

If you balk at 25 pound order, look for friends to share in it and take shares.
Stored properly it will be active and usable when you and I are not if you have concerns for "powder life".

Try Buffalo Arms:

https://www.buffaloarms.com/black-powder