We have been taking our cat with us camping for the last few years. Gertty is 8 years old now and mostly sleeps and attacks my toes if they wiggle out from the covers at night.
We use a retractable dog leash with e harness when she is outside. At first she did t like it on her, but now she stands at the door waiting to go out. We just put the harness on her clip the leash on her and clip that around something so she can't fly the coop so to speak. I added a large carabiner to the handle of the retractable dog leash so it's easy to tie her off to something.
We also have that large pillow on our console of the truck when we travel.
Only thing we hate is the Cat Hair..... but wife has a cordless Dyson vacuum that does a bang up job.
Soup.