P22s are great pistols to suppress. The adapters for the barrel nut are easy to find and cheap. To keep it quieter, you can put your thumbs against the front and rear serrations on the slide and hold it closed, removing the sound of the action cycling.
You might register and look here.
If you can buy a handgun, you can buy (or make) a suppressor. You can own it as an individual and go through a small bit of hassle, or you can own it through a corporation or a trust with some advantages and a lot less hassle. Some folks pay lawyers a couple hundred bucks to establish a trust, some use Quicken software to do it for $40 or $50 or so, some employers offer them as a free service. My tax lady did mine along with my taxes and some will stuff. Most corporations or LLCs require some kind of annual fee and if you should ever dissolve the corporation you must pay the $200 tax to re-transfer the suppressor (or other NFA item). Trusts are usually free forever.
BTW: NFA FAQ