I have used RVT.com and rvtrader.com. in the past. RVT has a one time fee until it sells. RVtrader is monthly. It is a perfect time to sell and they both have national exposure. Not everyone knows about Expedition Portal. Just the cool people.
Wander the West sells them pretty quick when priced right. Have you seen the @UsedFourWheelCampers on FB and Instagram. Maybe it could be posted there as well?