I'd just generally search online. Pawnshops and such are good too. Might be about the only thing left. No one wants good old revolvers. The M64 and 65 are easier to work with as to the finish, just bead blast. But the front sights are shiny stainless. Don't forget the Ruger Service-Six and Speed-Six. Both fantastic guns and actually popular worldwide for foreign police agencies. However they have been "discovered" by savvy shooters and often command premium prices. The old Colts are cool guns but not near as many Gunsmiths around that can still tackle them. Then there was the S&W 581 and 681 fixed sight L-frames, a premium find today.
Of course there were the alloy K-framed S&W too, M12, 13 etc. The K-frame S&W is plenty beefy to handle my old +P .38 loads and shot about point of aim with it and the 158 gr.