We wanted to rent Atvs so we used Awesome Adventures. They are a booking agent for Law Powersports in Overton/Logandale. Over all it was an amazing adventure.
If you want to save a couple bucks you could probably book directly with Law Powersports.
Highly recommend renting their GPS, it comes preloaded with a route that will show you the highlights of the area. Jill was the one that helped us and she was very nice and explained everything.