Pistol magazine pouch.

I am a fan of dedicated gear specific to your equipment.

But for overt carry, like on a battle belt, these are great. Kind of a hybrid. The plastic makes for easier RE-insertion under stress with angled feeding lips for the pouch. The bungee cords make for adaptability with different brands of mags.

 
Another vote for kywi pouches. If you're handy with a heat gun, you can adjust retention yourself as well. Or if you get them with a molle front, you can throw your own shock cord active retention on as well, if you feel like you need it.