With a 40B, which uses the same mags (but with a different base plate), I had good success with EAA Witness .40 factory mags. In a few of them, I had to enlarge the top of the mag release notch, so that the mags would lockup properly, etc. I've used them as 9mm mags, too.
Check CDNNInvestments.com.
While the factory mags are clearly superior, the EAA mags are pretty good, and a LOT cheaper, if bought from sources like CDNN.