At over fifty dolalrs a piece, I was having trouble getting extra mags for my Bersa 9mm UC Pro, which is what I carry primarily. So I found inexpensive mags that would fit the gun and made a minor alteration to the mag latch opening so they hold in the gun. Tested them at the range and out of four, only one needed further adjustment to work flawlessly. It allows me to carry fifteen round extra mags which will feed my little thirteen and one tool.
The process involves finding out which frame the gun is based upon (as in Taurus makes an exact copy of the Beretta 92F, so I have altered Beretta 30 rounders to work perfectly in a Taurus 92AF), then find the after-market mags which are available at a fraction of the 'factory' mags, and line up the mag catch hole position and dremel it out.
They're spendy, for sure. I have two spares, and would like to get more, but I get to thinking with a concealed sidearm, do I really need them?
Scouts Out! Cavalry Ho!