You might even consider selling it and getting a Colt AR-22. They have the same threaded barrel dimensions as a Walther P-22. You can buy an adapter to 1/2x28 for about $20. A standard real or Fake Can would just screw right on, then.
BTW...Threading is usually between $75 and $100.
Good Luck
brother I am not doubting your comment at all, I wanted the colt version also, haven't bought either one, but have seen ALOT of bad reviews on them. No idea why specifically but so far the M&p .22 seems the best option if a guy wants one. your mileage may vary..