Rescomp makes that mag catch, I've yet to try it on my kimber though (i opened the hole with a file). My para mags have ran flawlessly.
The new polymers dont feel as good in my hand, compared to the old ones built on the BUL M5 frame. And my Kimber Polymer DOES fit leather 1911 holsters, it does, however have the round trigger gaurd but still wont fit fobus, or other plastic holsters.