We bought a small-dog soft-sided carrier, with screened windows on 3 sides and a strap to enable fastening it in with a seatbelt. There's room for our cat to sit up, stand, turn around and otherwise be reasonably comfortable in it, yet she's relatively safe too. She is not comfortable riding in the truck (probably never will be) and prefers to be in the carrier while we're driving, rather than out of it (we tried both). We also have a harness & leash on her when we're underway, though not in the camper itself. She's an indoor-only cat at home, and stays that way in the campsite as well. So far it's worked out pretty well, though we are told all day long that she would rather be home. :)