Henry Kranks at Pudsey, Leeds for anything black powder. If your new toy is a .44 Lepage like mine i use a .435" ball with .010" patch. I find 18 grns of Kranks med or TS2 powder about right but you will probably have to experiment to find your own guns preference.
Nice LePage, i used to shoot my mates Pedersolli LePage and also his Kuchenreuter which was a very lovely thing indeed.
Mine is nothing nearly as special, just an old "Tingle"
Ugly old thing but it's supposed to shoot well, time will tell