General Purpose Housing Adapter underwater camera housing One of the easiest way

One of the easiest way to achieve that is by using this 9 -24v adapter that fits right into the GoPro®'s internal battery space

As you can see

Outside diameter is 3" (7

5" long (27cm)

Benthic Extension Module's features are:

General Purpose Housing Adapter underwater camera housing One of the easiest wayThe General Housing Adapter is made to link together several GPH 1750m series (not for GPH 2800m or GPH 10) . Suppose you want to add several control boards and a large battery pack to your video camera or flashlight set up. By adding this adapter ring, one GPH could be dedicated to storing batteries while the other GPH houses your control boards. Several GPH can be safely attached together this way. OD: 3" (76mm) ID: 2. 32" (59mm)