Well the best option is a Uberti cylinder. These are available from VTI (vtigunparts.com) as well as the Uberti sellers like Cimarron and others.
Any cylinder copied from the 1st and 2nd generation Colt, including Colt, can be fitted. Length issues can be overcome by setting the barrel back (for shorter) and cutting back the breech end of the barrel for longer cylinders.
I would also purchase a new cylinder bushing to be fitted.
I have a few NOS BP 1873 cylinders (with nipples) if anyone is in need.