I noticed that problem with my MK40 mags, but my P40 mags don't do that at all. I don't think my wife's MK9 does it either.... Wierd.
But since you asked... I found a clip-on nylon mag carrier from CDNN Investments for $3.95... (I looked on the website, it's not there). It was in the catalog as being for "double stacked mags" but my Glock 19 & USP40 mags won't even come close to fitting.
I took off the metal clip, and it now fits horizontally on my belt using the web loop area the clip came out of. It's open ended, but the Kahr mag fits perfectly in there with just enough tension not to slide out unless pulled. It also works as a pocket mag holder, since it's so very slim.