Cheap? Like many have mentioned, look for a used Ruger MK II/III or 22/45. There are many out there that are in great shape. Even then, these things shoot forever.
I spent $249.95+tax on this LNIB specimen last month.
Last year, I picked up this Ruger 22/45 (with the optic sights included) for only $229+tax.
I'd recommend the Single Six as well, but you've already got revolver and plus they're generally not as cheap.