I've been looking for something similar for my FAL magazines, but so far have found nothing factory-made. Mad Dog used to make Kydex AR pouches, and I think that Comp-Tac does as well.
The Wilderness LLC makes a nylon mag pouch with a thermoplastic insert that might work. .223, .308, or 9mm.
Other than that, maybe some Kydex genius could whip up a short run of custom pouches. I'd buy a few.
- Chris