FYI, I just did a Google search on your year and model of Montana. I have a 2019 Montana High Country 375FL. Looking at the photos of your model, it looks like the same wheel rims hasn't changed for a few years. Check with your nearest Montana dealership. I'm sure they can get one for you that will match the other 3 on the ground.
FYI, my spare tire rim is all white, the 4 on the ground are the pretty aluminum ones. I certainly understand why you don't want to run on the spare tire any longer than necessary. We had a blow out this Summer and I put the white rimmed tire on the ground. Although functionally, it was a perfect fit, aesthetically, it looked horrible next to the pretty aluminum polished one.