I know that this is an old thread, but in case anyone searches or Googles it, there is another .22 WMR option in a semi-auto, made by Kel-Tek. It's a small 30 shot pistol, partly made from plastics. Here's the manufacturers link:

Kel Tec CNC

Disclaimer: I have never fired, or even held this gun. I just know of it's existence. I don't know whether it's good or not, and neither recommend it nor condone it.

Regards,
aeronaut