Chuck: Call Bain & Davis Sporting Goods in San Gabriel. Pete Stepanski is the owner and resident pistolsmith, and I know that he is a pretty serious black powder shooter. This is one of the few remaining, old fashioned gun shops with two (yes, two) gunsmiths on the premises (Steve Matthews does the long guns), and for those old enough to remember, is also the home of the wildcat .357/44 B&D conversions. That's a .44 Mag case necked to .357 for a modified Ruger Super Blackhawk or S&W N-Frame (although they prefer the Ruger for strength). Wowee!
You might also try Phillips Supply (reloading stuff and loaded ammo) somewhere around Azuza. If you can't find the listing, the boys at Ivory Beads can direct you to Phillips.
Lock, Stock & Barrel in Temple City used to have a lot of black powder stuff, so you might call them, too.
