Well, I actually found this thread looking for a solution for camera-bounce myself, as I usually just thread it through the chest-strap so it's not hanging off my neck.
But for quick access to lenses, I have two cylindrical top-zip barrel-bags with belt-loops that I attach to the hip-belt of my pack and put them WAY at the back, like hip-panniers. Except when I'm indoors and going through doorways, (when I slide them out front) this distributes the weight a lot better over my center of gravity while I'm walking than pulling me forward. It's bad enough the backpack and camera do this dance with my front-back center of gravity. The lenses/panniers kind of add some side-to-side stabilization, lol!
And I always keep my telephoto on one side (consistently), wide-angle on the other, and walk-around/mid-range in the camera, or swapped in whatever bag is empty/lens is in the camera. That way I don't have to think about where things are too much, and I stay organized.
I've seen bottom (tripod mount) clips that can either clip your camera to your belt or your shoulder-strap or chest-strap or something... not sure I'd trust that... and my next trip will be "where the sun don't shine" so I need rain-protection as well, as I'll be hiking more than shooting this time around. Luckily, I'll just be doing mostly landscape photography, so I don't think I'll need to quickly whip out the camera for a lose-it-moment, so I can probably rig up a fanny-pack or something to sit underneath my backpack, if on my chest or belly doesn't feel right.