As I am not carrying much gear, I use the little bag/sack that comes with the suction cup and keep it in my pocket.
Over time I found out that most of the gear I am carrying I don't use very often, and for most situations there is a good another solution.
When I need a gimbal then I get the cam gear into the gimbal case, but as said in most situations I don't need much gear.
You can pay lots of money for fancy bags or other containers, but I dug out from a shelf in my garage an old slim aluminium attaché case, the sort that can be bought cheaply from a variety of suppliers. I bought a block of pre-cut foam, trimmed it to fit, pulled/cut out various apertures in the foam for a couple of GoPros and a few accessories, and it was all done. Compact, goes into the car - though for mounting onto my kayak, when I go fishing I take the GoPros ready mounted onto Railblaza accessories, all ready to connect into the kayak's sockets. I just wrap pieces of bubblewrap around the cameras for transporting in the car.