I hate to say it, but a used Ruger isn't much more than $300.00 around here. Normally I hate the "save a little more and get something else" line, but in this case it's true because the OP set the bar rather high at $300.00. I've bought a Uberti 22 S/A in that price range too.
If you think used, you open up a whole world of other options. Just since Christmas I've bought two used 22's for less than $200.00. One was a Ruger standard semi-auto, and the other a High-Standard Sentinel, 9 shot, D/A revolver. No, they're not convertables, but I personally have never seen much use for a 22 Magnun. I've owned several with a magnum cylinder, but have never fired a single round.
(They were not "beaters" either.)
I suppose if I had to pick one of the less expensive new ones, I'd go with the Rough Rider.