Hi,
This seems to be more of a business strategy question than a patenting question so I am going to move this to a different part of the forum.
If it were me, I would try to protect the idea the best I could (perhaps with a provisional or non-provisional patent application) then get a few users to test the prototype and give feedback. Once you have a final design completed I would approach GoPro or any other company that is making GoPro accessaries and ask them if they would like to license, manufacture, and sell your idea and pay me a small royalty on any sale that they make.