We had good luck with
RV Trader, you can customize a search for what you are looking and how far you are willing to travel. Set alerts and save the search and you'll get a text or email when one that fits your criteria comes on the market.
Dealers advertise on there too, so when you go to the dealer you can start by saying "I'm here took at this specific unit" and the salesman is less likely to steer you around. Also keep an eye on Facebook Marketplace, that's another popular place to sell RVs.
Once you see what's on the market you can decide if you want to expand the radius, modify the criteria or wait until something comes up. We looked at a handful of units, and it took about a month for the one we bought to come up in the search. The unit you want is out there, but you won't find it at just one dealer.