I have had several folks tell me them "extry" .45 ACP CONVERTIBLE cylinders are prevellant at gun shows.
I ain't never been able to find one that way.
You might try Ruger. Last I heard they will still factory fit ye one in a
Blackhawk .45.
The OM Vaquero uses them same nominal cylinder dimensions.
You might have to sweet-talk 'em into fittin' one for you.
Last one I had done was in about 2000 or 2001. I recollect the bill was $110.
Good huntin', Pard!
MG