Part of the standard issue US Molle II system: 9mm Magazine pouch (single). Aka, the pistol magazine pouch.
These are in ACU/UCP (that grey digital camo that blends in with a gravel pit and grandma's couch)
NSN: 8465-01-524-7361
These feature a single flap with metal snap, and will hold a 9mm pistol magazine. They are meant for US M9 (Beretta 92FS) magazines but will work with most other pistol magazines too, providing they are about 15/17 rounds in capacity. Would also fit most smaller sized flashlights.
These will be from a variety of makers, but all are genuine US Government issue and in excellent shape.