Flasks that are made to look like cartridges by Jack Pyke are available at the Military 1st online store... "The Jack Pyke Cartridge Flasks are in stock now at Military 1st. Made of sturdy 18-8 stainless steel, with vacuum-insulated walls and press button pourer, keep your favourite beverage hot for hours when out and about. 

These insulated flasks are perfect for shooting enthusiasts.

Knight's Armament just made available one of the must have gear, according to us here at Popular Airsoft and as soon as we tried to order, the stock ran out. Bummer... "Enjoy your beverages in style with the KAC SR-25 Magazine Flask. Modeled directly from the dimensions of a issue SR-25 Magazine, this is a custom in-house design only from Knights.