Ammo for a .41 RF. Gunshows. Figure a couple bucks a round minimum, and figure that since the stuff is 50-80 years old at the very best, it may or may not work.
There was an outfit in France making cartridge adaptors that used an Acorn Blank (good search term, if the search engine decides to work for you), to ignite a small charge of black powder under a round ball.
Dunno if they make them in .41, but the idea is still good. May be possible to track down someone to make you a few.
Mostly, though, shooting a rimfire other than a .22, is pretty much a 'burn your money' kind of thing. Then, only if you can actually find any ammo.
Good luck!
Cheers
Trev