Great storage! - SureFire One P60/P90 Lamp Assembly Spare Carrier

Holds 6 CR123 batteries which in my case is a full reload to Rifle/Shotgun/sidearm light batteries. It’s super durable, the lanyard it comes with had two adjustable devices(can’t think of the name) to keep/use with your needs, also comes with a small Quick attach loop.

This thing can be banged around just as much as your duty pistol/rifle, it’s water resistant/proof as well... highly recommended keeping one of these with batteries in your backpack... also I don’t use it but for extended period guys(deployed overseas or Tier1 maybe) you can store a light head if needed as well).