Ruger made a sweet single shot pistol, known as a Hawkeye, in 1963. It is built on a revolver frame, but instead of a true cylinder, it was a breech block, that pivoted open when unlocked, allowing a single .256 Win round to be inserted. Close the breech, then cock the SA style hammer & fire.
It's not a break action type like the T/C, but it is a true single shot.
Production was about 3300 guns, and they are highly sought as collectors. Some are even shooters,,,,,!
PS; They aren't usually "cheap" to purchase.