Australia-based Earthcruiser builds extreme overland-style campers and now sells them here in the U.S. The campers are Mitsubishi Fuso–based, but Earthcruiser modifies the suspension so the springs offer more flex and axle articulation for traversing rough terrain. The camper has a diesel cooktop and 90 liters of fresh water, and an additional 100-liter tank is available, so you could have one for showering and the other for cooking. –