Black powder isn't a gun store item anymore. But it's still very available. Several of the distributors are selling on line. They will also sell you as little as five pounds mix and match.

One such company in your area is Powder INC. http://www.powderinc.com/ Look very closely at Powder Inc's prices, they include shipping and hazmat fee in ther per pound price.

The is also a black powder distributor in Advance NC just north of you, go to http://www.goexpowder.com/distributors.html#nc for details.