Magazine Fit

I just brought two after-market magazines from Marstar. Both hung up BADLY and wouldn't release. Fortunately, they were empty, I had to take the grips off and force them out with a screw driver. My original mag works just fine. Needless to say, I now have a full appreciation for the importance of quality Luger magazines. Can any one recommend repo mags by brand (and what to avoid)? Also, what is the going price for orginal surplus mags and, as a practical matter, can you find them?