Winnebago issued the camper with dicor hubcaps and I had alot of problems with them flying off from one side of the rear wheels. I talked to one of the wheel simulator companies and they said that was a frequent complaint with snap on hubcaps on a dually setup. I did call dicor but they were not much for customer service. Winnebago did issue a replacement pair of snap on hubcaps to me which did not solve the problem as one of those sailed off into the sunset a short time later.
I found the site above recently and bought a pair of simulators for just the rear axle. They are very reasonably priced and are mechanically fastened so no more lost wheel covers. The quality is good and the dealer is friendly and helpful.
I wish I found them a year ago.