If you need enough to offset the $22.50 HAZMAT fee, check with Natchez, if you look around at the price/availability of powder locally, it doesn't take much to justify the fee.
You might also check with Phillip at the Indiana Gun Club (317)-485-6540 he might have the Blue Dot powder in stock but since he mostly deals in shotgun related reloading components I doubt he'd have the Power Pistol.