A great tactic i picked up from some real guys is to have a strip of velcro on the torch to attach it onto your helmet. Its easiily accessible, adjustable and pretty secure. If it gets knocked it falls and doesnt rip your lid off, (not so much airsoft but important in real combat) it can also be removed an placed on a PC or in a pocket.
Remeber a torch should rarely be used in a fire fight, it gives your position away and screws up your vison. Keep it only for doing tasks such as objectives, searching, repairing or restocking or treating casualties.