There may be a problem with some local shops selling blackpowder as the cost of meeting the requirements may be more than the actual sales add up to, what with folks thinking they're better off with the fake stuff.
There is also a shortage of Goex powders at the moment as there's been a rash of explosions in the last couple of years at the plant, that have really messed with the availability of civilian/sporting grade powder.
There's no place I know of within a 100 miles for me to get blackpowder, so I order from Powder Inc, Grafs and sometimes Bear River Powder. In addition Track of the Wolf, Maine Powde House, Buffalo Arms and Upper Missouri trading co, and Coonies sell black by "mail order".
Also Powder Inc , Grafs and Buffalo Arms will ship in as little as 5 lb lots. And Powder Inc's prices are delivered .