You might try El Monte, the other nationwide RV rental place, but I think you are going to find a certain amount of bad press for all of them. Those rental RVs get used hard and it's difficult and expensive to keep them in top notch condition. Mostly you have to hope to get a nearly new one rather than one about to be retired. The more expensive rigs may be in better shape, if your budget will stand it.
Try a Google search on "rent motorhome" and you will get lots of hits. One of those places might be in your area and have a nice rig available in your timeframe. Problem is, though, they are seldom sure exactly what rigs will be availble in 4 months down the road. You may not get the rig you were promised, despite their best efforts. Accomodating breakdowns, schedule changes, etc. raise havoc with the best laid plans.
2004 American Tradition; 2014 Buick LaCRosse
Homebase in the Ocala Nat'l Forest near Ocala, FL