Here is a kit with everything you need to build your own off-road rover. The Mini Mantis 6WD Off-Road Rover comes with 3.85” aluminum beams, 4.3” off-road tires, and 485 rpm Economy Gear Motors. You get mounting and customization options to take your rover to the next level.
As you can see in the above GIF, the rover is capable of negotiating rough terrain. Costs under $300 at this time.