I can't help you with getting a good deal on renting an RV, but I wanted to let you know if you have a few days, you should camp at Waterton Lakes in Alberta Canada. We did this last year and this place is beautiful. We started in Yellowstone, drove through Glacier and then into Waterton. We were trying to go to Banff after Waterton, but we ran out of time! It's part of the International Peace Parks with Glacier NP.