"Kirst Konverter" is a 5-shot .45 Schofield conversion for the 1860 Army.
Kirst Cartridge Konverter for Pietta 1860 45 Schofield Cowboy Gun
You can use a Dremel tool and cut/file the frame out on the right side and use the loading gate with the Kirst Konverter if you buy the ejector that replaces the loading gate:
Kirst Cartridge Konverter Ejector Assembly ONLY for Uberti 1851 Percussion Cowboy Gun
The R&D conversion cylinder is a simple drop in and doesn't have a loading gate.
R&D Cartridge Conversion Cylinder Engraved for 1860 Pietta Cowboy Gun in 45 Long Colt
Both of them usually need just a bit of filing with a needle file on the ratchets to fit in the gun- just like fitting another percussion cylinder.
I wouldn't recommend trying to get this shipped from the US to France...US customs would likely get it if the shipper wasn't up on the laws of the "international transport of arms act" or something like that.
Also, the shipper would likely have a knock on his door from the US State Department or Commerce Department if laws weren't followed.
I do believe that Brownells sells these cylinders, and they do more international shipping of gun parts than any other company in the US- they can answer the question if they can ship that to you.