Yes. The Kirst Konverter.
www.kirstkonverter.com. However, it requires that you cut a cartridge port in the recoil shield of the revolver. This is a modification the ATF considers as creating a firearm. You may have it for personal use but may never sell it. Kirst also sells an ejector rod to mount on the 58, which required a notch in the loading lever to retain it. However it is interesting to point out that reloading with a second cylinder is significantly fastrer than reloading through the port ala Single Action Army. (7 seconds against 20 some). The Kirst can also be mounted without cutting the port, but it would then require removing the cylinder to reload as with the R&D. The Kirst has 5 chambers and a false safety position for CAS shooting, so it is a 5-shot in 45Colt. He makes it as a 6-shot in 45ACP and 38.
