There are batteries made specifically for CPAP travel. Cost runs in the hundreds
I have traveled many thousands of miles with mine and used mainly in hotels but I have camped with it as well. I am simply limited to either camping spots with electric (State Parks) or RV spaces like the one I shared with Richard at Spearfish
I just got a new machine that comes in a small satchel and will fit either in the left pannier or the bottom half of my top box
The actual machine is no larger than a clock radio (if you don't use the humidifier)not much more area than a large hand...5" x 6" x 3 ". The cord with transformer, hose and mask create the need for more storage space
It really isn't that big a deal for packing; 672 cubic inches 12x14x4 is what I give up to take the CPAP
Again, it equals either the left pannier or half of your topbox
You could also store it in a waterproof duffel on the backseat