I have had a Peli 1120 case sitting around for a short while. I have been meaning to get it kitted out to hold a small selection of my GoPro kit.

I have set the foam up to accept:

The GoPro in its case with bracket attached
2 x spare batteries
1 x spare mount
1 x spare bracket

I have enough room to carry a few more mounts or batteries plus loads of SD cards.

The case is small enough to carry in most boats either behind the seat or in front and is an ideal way to protect your kit during transit.