Rim size

[markarbogast]

I have a Coachman Sportcoach Cross Country (2007) 382DS DP.
It takes 235 80R 22.5 Michilen XRV tires. I have a new unmounted spare and I would like to search for a rim but I dont know the size.

[TBS-POPS]

22.5 standard dual wheels come in 7.5-8.25 and 9 in width. Most common is the 8.25. Check the wheels on your coach to make sure you get a matching width wheel. Also being a 2007 it would also probably have stud pilot wheels. Check existing wheels also.
A mounted spare is heavier and harder to handle than an unmounted one so unless your changing your own flats, road service can mount a tire just as easy as changing one.. FWIW I have never carried a spare, never had a flat. ( now I'm doomed).
Also an aluminum wheel is tons lighter than a steel one. Accuride is a manufacturer of alum wheels so you can check the different styles of wheels. A truck stop with tire service can get you a wheel new or used or any tire dealer that sells truck or motorhome tires. Good luck!