By dick from NS
You could try one of those sonic repellers but no guarantee it will work. And it would mean keeping your RV powered. I would recommend putting poison pellets around under the cabinets and other areas you would expect mice to roam.
As a campground owner, this is what we find works: put strongly scented fabric softener sheets all around in your rv-on floors and furniture. Put moth balls all around the outside and below your rv. Some people also put moth balls inside, but it's hard to get that smell out when you want to use your rv.
When I had an RV and lived on a farm, I found that the most effective way to keep mice out of the RV was to park it close to the house where we had dozens of outside cats. We tried the mothball thing, and that didn't work, and also was a terrible smell in the RV. The cats, however, kept the mice away.
Your perfect solution is the cat/cats this eliminates all toxic substance harmful to humans and animals.