I have been using the belt shown in the link here for two years now,
http://www.frankproctorshooting.com/proctor-covert-belt-black/ it has been the most comfortable way for me to carry an extra mag, smallest being a single stack mag for an cm9 to my regular mag for a glock 19. Don't think any of the mags are going to fall out either! This belt allows me to carry an extra mag and a ZT0350 without anyone knowing I have either. This has been hands down the best investment for my CC I have made. I am about to order a new one as after two years the bands that hold the mags have started to fray a bit. I expected it to go sooner as I insert and pull my mag every day in order to get the belt on and off. Even with the elastic being frayed a little where the mags are inserted, one has never slipped out. I have even used one of the spots for an extra 223 30 round mag while walking around in the woods. You won't be disappointed!