Of the three barrel lengths of stainless .45 convertibles, the 4-5/8" is the most "common". Ruger made 355 of them. That's the large frame protected sight version. They made 320 in 7.5"and only 77 in 5.5".
They may have made more than that of the recent flattop convertible, but even those are fairly scarce.
If you would consider a blue gun, I have a 1976 "200th YEAR" liberty 4-5/8" convertible in the box with shipper, model BN44X. It would lean toward the expensive side.