bj426, If you live in the USA and are not a military or LEO, the answer would be no! Since the ban in 1994, it is illegal to manufacture or import magazines that can hold more than 10 rounds and make them for sale to civilians. We were able to get a limited number of hi-cap mags for the P99 because it was just being released at the time of the ban.
Besides that, I won't be surprised to find that the magazine in the P22 is a skinny single stack that would only hold 12 or so rounds even if there wasn't a ban. All .22lr pistols seem to share the same magazine design. Also, from what I understand, the grip on the P22 is considerably smaller than that of the P99.
What I do find interesting is the two different types of mag bases. The 5" model appears to have a finger lip. While the 3.5" model appears to have a square base. Why have two different designs? Why not just standardize?
-Red-