I managed to get a free one (mag loader) a while back as part of a promo. When I got my last P99, there was a special to get a free mag and magloader.
U should call Walther USA and see if U can buy this. It is almost like the Glock one.
I don't use it, but as it is not a very common item (they don't put it in the box like they do with the Glock one), I really don't wanna part with mine.