The forums have a good classified section. You can also look on craigslist: san francisco bay area classifieds for jobs, apartments, personals, for sale, services, community, and events
but you have to look in every city. I've heard there's a new search function will report all listings for a certain item, like "airstreams", but I haven't used it.
I'm assuming you are willing to ship one from the States if you find what you like.
There are several European members who are active on the forums. One in UK, one in France, and one in Germany, that I recall, but I think they all have trailers, not motor homes.