I use an Uncle Mikes kydex double stack mag holster and it works well. Mine holds two. I have heard some say that the singles are better. I don't know.
I use mine for IDPA BTW. Fobus makes some as well.
I am using some old Ernie Hill Speedleather pouches I picked up cheap years and years ago. They work fine, and I think I have a whole $25 in 3 of them......
I use the Uncle Mike nylon double pouch (with snaps) that is formed for regular 9mm abd .40 double stacks. Simply remove the retaining straps and the double stack .45 mags fit snuggly inside. Hope this helped.
Semper Fi!
-L7