Just drive along some of the interstates and pick up a set from side of road. See them out there all the time, some look 'new'. I would not use the rv to look but just drive around some. Particularly on the road from I20 to alexandria to look that is a place that will shake anything off.
Front or Rear? For RV's it seems the term "Hub Caps" is to cover only the Hub area. "Wheel Covers" would be a Disk (big Frisbee) that makes the rear wheels look like the front wheels. "Wheel Simulators" are two sets of two. Two fronts that are like "wheel covers" and two rears that dish "in" to correspond to the outer dual wheels. I looked at Amazon where there was a variety of covers and simulators. I suggest you stay away from "snap-in" covers and sims. Get something that has positive attachment. Some kind of threaded fasteners. Otherwise you'll be looking for more soon.