I've been told you either have to enlarge the top of the slot on the mags by 1.3mm, or order the replacement mag catch from Rescomp in South Africa. I'm not certain whether or not they still sell it; I tried emailing them, and got a failure to deliver email. It is, however, still on their web page, and I know they're still in the gun belt and holster business, at least.
Do not mistake precedent for justification.
Doubt is an unpleasant condition, but certainty is absurd. Voltaire