Nice pussy! Not every cat has the temperament to become a traveller, but start by getting a body harness lead and take it for frequent walks, try to introduce it to everyday situations without causing stress. If this is successful, introduce it to travel by either giving it a dedicated seat and tethering the lead or using a cat travel box. Again, there is no guarantee that the cat will accept this. Next step would be to introduce your cat to outdoors where you are camped, firstly by taking it for walks and secondly by tethering it by your van. In some cases, if in a remote area the cat can be trusted to roam, (but at some risk).
We did this with a cat acquired when we were first married where my wife wanted a cat and I wanted a dog, of course my wife won, but the compromise was that we would train it like a dog and it worked; he accompanied us on all our UK holidays for 15 years. On his passing, we acquired a second cat and tried the same tactics without success, that one spent more time with friends while we were on holiday than it did with us!
There is someone on this forum who travels with a cat who might be able to advise you.