Nuprol Dummy Laser battery box.

The NUPROL Mock Laser is a lightweight, inert prop designed to give your replica a convincing tactical appearance. Engineered to clamp to standard RIS rails, it delivers the silhouette and controls of a real laser module while remaining fully non-functional out of the box. The unit includes an internal storage compartment sized to accept a spare battery or small components, providing tidy on-replica storage or a simple way to retrofit electronics later. Constructed from impact-resistant polymer with a hardwearing finish, the mock laser withstands knocks and transport while adding minimal weight to a setup. Batteries and electronics are not included.

Please note this is an aesthetic item, and whilst it does have space for a battery, it is unlikely to fit one that will power your hun.