I actually used this idea originally with a small video camera, but it works quite nicely as GoPro storage in a larger camera bag to prevent it from getting scratched. Behold, the GoPro sock camera case:
Although I’ve never seen the “sock case” anywhere else, I’d be willing to bet I’m not the first to try this storage method. If you’re wondering about the larger DSLR sling shown in the background, here is is from Amazon. I generally put the “GoPro storage sock” inside the top compartment, so I have both cameras with me. The sling is a bit more expensive than a sock, but it works quite well for my needs.