Savage also made a single shot 22 pistol in the 1950's and/or 60's. It was called the Model 101, and was styled to look like a Colt Single Action Army, although I think it was more the size of a Ruger Bearcat. I think they made more of them more of them than Sheridan did "Knocabouts". (That is the way Sheridan spelled it. I am sorry.)
There is an article about the Knocabout (wince) here:
https://www.guns.com/news/2013/08/10/sheridan-knocabout-the-lost-22-pistol
And one about the Savage 101 here:
https://www.americanrifleman.org/articles/2010/5/27/savage-model-101-revolver/
As I understand it, there used to be an organization called the US Revolver Association which held important competitive shooting matches. Despite being a
revolver association, some of the matches were for single-shot pistols. This led to the development of high-grade single shot pistols, like the S&W revolver conversions, the S&W Straight Line, the H&R USRA Single Shot, and maybe the Colt Camp Perry. When those matches ended, the demand for such guns dwindled away until it was so small only custom makers bothered with it. Immediately after World War 2, a number of makers tried out cheap single shot 22s as kind of beginners pistols for young people. I don't think any of them were made by established pistol makers. I think the Savage lasted the longest of all of them.
So I guess to answer the question asked in the title of this thread, nothing made now is comparable to the old 22 single shot target pistols. The demand went away. There are plenty of single shot pistols, and you can probably get 22 rimfire barrels for some of them, but they are mainly intended for hunting or long range target shooting with centerfire cartridges that range from .221 Fireball to handcannon stuff I don't even want to think about firing.
I wrote all the above just off the top of my head, and I look forward to the errors being pointed out.
Oh, I should add that Hopkins & Allen also made a single-shot 22 based on their 38 Safety Police frame back before 1917. It is probably even scarcer than the Smiths now. IIRC, Iver Johnson did not have a horse in this race.