ok, i just bought an aftermarket stainless cylinder from brownell's to have fitted to a 44 mag stainless vaquero, it will need fitted and chambered. The cylinder was $180.00 and I'll probably spend at least $100.00 more.
I also bought a blued engraved 44 mag cylinder from a Bisley and it very luckily fits perfectly without adjustment on a 44-40 vaquero stainless I own. I gave $75.00 for the cylinder on gungroker.
like others have said--- probably the only person who will be interested in it is someone like me. I shoot cowboy action with bisley vaqueros in 44 mag. now and I am putting together a set of 44-40/ 44 magnum convertibles to shoot. With the 44-40's the frontier cartridge class with black powder, then with 4 vaqueros in 44 mag, I can shoot Josey Wales and I use my standard bisleys to shoot 49er class.
My guess is the cylinder would sell quickly at about $100.00.