As far as rentals, the only other one I've heard is Cruise Canada but I have no experience with either.
As the previous poster stated, you're nearing the end of the camping season but you should be okay. If you are looking at stopping at Ontario Provincial Parks, you can see here (
http://www.parkreports.com/openclose/index.php?year=2013)that most of the 'non-winter' campgrounds close on Oct. 14 or Oct. 15th. You should be able to find private campgrounds open around those dates but they'll probably be closing around then as well so you'll probably need to plan the tail of your trip pretty carefully.
Last year I did notice that some companies had cheap rentals to 'return' rvs at the end of the season (can't remember if it was East->West or West->East) but that could be an nice option especially if you could extend your trip.
