Hi Johan, it is possible to fit a shower tent. You should have a Company near you that can manufacture a shower cubical for you wich can cost in the region of R3500.00. To make this work you will have to fit a water tank, water pump, geyser and plumbing adding more cost.
Another option is to purchase a foldable shower cubical that you can pitch near your van, a 6L portable gas geyser that has a buildin 12v water pump, 4.2 meter ose with shower head and the option of adjusting the water temperature. You can then fill a 20L water container with water, place the suction water pipe in the container, connect the geyser 12v to vehicle or caravan battery and Bob is your Uncle.
Regards, Dirk Botha.