I know Pest Control companies will be willing to set up your motorhome for a mouse free winter. Mouse control
can always become a challenging issue that seems like a never ending battle!
I know of a company that did my house for bed bugs last year and they were really great. I'm sure not exactly how it works with mice, but with the bud bug issue I had, they never came back,
If it;s something that can be afforded, it's definitely worth it. Environmental Pest Control.
Hope this was somewhat helpful! Unless you were looking for strictly DIY method :s