Walther P1/P38 extended magazines

Hey, I am kind of "stuck" with a Walther P1 that I overpaid for a few years ago, when I was still pretty naive. I feel really bad when some guns don't get the attention they deserve, and I presently don't have much use for this. Which begs the question, since the only other handguns I own are lightweight compacts for carrying, can my P1 be reasonably pressed into competition service? I'm not trying to win, but I also don't want to kneecap myself too much.

Obviously, capacity is its biggest handicap. Does anybody know about whether or not there are mags out there, offering greater capacity, that can be modified to fit my P1? Or if there are gunsmiths out there able to weld mag bodies together? I saw that a store in New Zealand sells 15 rounds mags, but there aren't details on the manufacture or any reviews and for $279 shipped to the US, that defeats the purpose of this entire idea. Thanks!