I spent 6 mo looking for mine utilizing RVT.com, IRV2.com, the Escapees for sale thread, RVTrader.com, craiglist.org and a craigslist aggregator (but I don't remember which one) and pplmotorhomes.com. I kept a separate window for my RV hunt with a tab open for each of the above so it was easy to refresh daily. Once I got focused in a several brands/models that I was interested in, I added google tabs for those with "Make model RV for sale". I found very few dealer used rigs that were remotely as clean as they described. I finally discontinued the PPL link since they steadfastly refused to answer questions and I wasn't about to travel 1200 miles to see a consignment rig based on their standard 1/2 dozen pics with formulaic descriptions. I found I couldn't trust their representations having paid an independent RV inspector to look 3 times at selected units on their Houston lot.
I did end up buying from a private party about 200 miles away via a Craigslist posting.