Blue Force Gear, typically involved in the construction of loadbearing equipment and excellent slings, is releasing its holster to the public (it has already seen combat use in Afghanistan). It's designed to carry the 40mm M320 Grenade Launch Module with minimal weight and encumbrance to the operator (it weighs in at less than half a pound and doesn't take up much loadbearing real estate). The open-top holster mounts a 3 x 4 MOLLE field and can be mounted either right side/grip to the rear or left side/grip forward. It features an adjustable cross strap for use with any sighting system the particular M320 might be using and is equipped with a bungee retention loop for the grip.
One feature that may prove well-liked is its ability to lie flat when not in use, saving storage space in a pack, bag or vehicle. It certainly beats carrying the 320 in a SAW pouch or other field-expedient holster.
Buy yours or a few for your platoon at http://www.blueforcegear.com/m320-grenade-launcher-holster/
M320 seeing some use: