You may have to kick up the size of the spare tire but I would just reuse your 17" rim. Look for a tire roughly the same diameter as your 19.5" ones. As Kohldad mentioned, if you have a rear blowout, take the front tire off and put it on the rear. Seeing as so little weight goes on the front axle with a camper, you won't have weight issues with a standard tire with 17" rim on the front. As mentioned, I wouldn't be doing a nascar race with a somewhat mismatched front but I'd feel comfortable to do a few hundred KM's at a slightly slower speed