When I needed wider wheels on the '02 DSDP I just went to a truck wrecking yard and picked up 4 9" X 22.5 Alcoa wheels and 2 9" X 22.5 steel wheels. Had the Alcoa's polished at a truck wheel polishing place. Cost me $35 a wheel since they were pretty pitted. Then I had them mounted when I bought new tires.
The 9" width is pretty standard for trucks, anything narrower will be tough to find in a wrecking yard.
2009 45' Magna 630 w/Cummins ISX 650 HP/1950 Lbs Ft
Charter Good Sam Lifetime Member, FMCA, SKP
RV'ing since 1957, NRA Benefactor Life, towing '14 Jeep JKU Dragon Edition