Handle Toolbox
The Handle Toolbox fits with the empty space of a MOE (Magpul) handle.
A small toolbox holds 2 CR2032 for the red dot sight recommended above and 2 14250 batteries for the laser. As a bonus the allen wrenches used to adjust the red dot sight and laser slide into the base of the toolbox.
The toolbox is tapered in a way that allows it to slide into the reliefs of the handle's bottom plate.