Airsoft Atlanta got the The NcSTAR Tactical HPA Air Tank Pouch Molle Pouch for you to easily carry your HPA tank with your gear that is equipped with MOLLE loops... "The NcSTAR Tactical HPA Air Tank Pouch Molle Pack. Fits on all Molle webbing setups - back of vest and other packs, depending how you want to mount it. Can be used on a belt also. Fits ALL tanks we could think of: 13/3000, 48/3000, and the 90/4500 is a tight fit, but still works.
The top will not zip closed on the 90/4500, but it will on the other types, depending on your regulator's size. It has two zippers on top, so you can close it most of the way and still allow your external air line to come out. Very high quality setup with extra pouches, molle, and other attachments. Bottom hole for draining if it gets wet. Can be used for other things, but we found the HPA tank setup works best!"