We used to have freinds that would come on holiday with us with their cat, both in a tent and a caravan.
Was OK the first few times, but then the cat went walkabout on the day we were due to leave. We'd packed, waited a few hours whilst they searched the woods etc, then they packed, then searched again. Eventually we all left, but they turned round 20 minutes later and hung around for a few more hours til he showed up. Stressful, and really messes your day up!
Plus, what if its hot and you want to go out for the day or a meal? You can't leave the cat in a hot van.
I'd have to say, the best option would be find some friends to look after it…or pay someone you don't know!