I assume you envisage a gravel van and not an off-roader or 4×4 because most tend to be fairly heavy. I also assume you have discounted a single cab bakkie with a roof top tent.
That leaves the “GRAVEL” Vans and the 2/3 bed versions are fairly light, i.e. from 800kg to 1.100 kg GVM but offered types/models are fairly scarce compared to the other abovementioned types
You MUST have a towing vehicle which is equal in Tare weight to the caravan but preferrably a bit more. Since you do not want a biggish vehicle, like a double cab, a single cab bakkie is the answer (towing capacity in kg, engine capacity in kW and engine power(torque) in Nm) The first and the latter parameters are very important since they determine which van you can to tow reasonably comfortable (weight).
Space for your camping /travelling gear is also very important, hence the single cab….
The heavier the van the more Nm are required (together with kW).Luckily , todays bakkies are offered with for example 2l Diesel engines , delivering sufficient torque combined wit sufficient kw. You could also elect to have a petrol engine but bear in mind that engine capacities being equal Diesel engines deliver the higher torque at low revs. therefore towing with a small to medium sized petrol engine (e.g 1.6 to 2.0 litres) will not result in pleasurable towing, particularly on longer trips (more than 200km) and with lots of up-and downhills..
The word towing pleasure is my own creation , because I once towed a small ,normal
caravan (GVM 750 kg) with the original Merecedes A-class 160i in Petrol. The car was a manual and I took the combination to Namibia for 3 weeks. There are not many up-and downhills there but quite a lot of wind. My car had a very bad time with an angled headwind for approx. 400 km on the way in and later again – ON A LEVEL ROAD -and I had to gear change between 4. and 3. and could not even maintain 80km/h. The 5th gear rusted solid !!! (If memory serves me right the old 160 petrol A-class delivered 90 or so kW and 17o Nm.
There you have it BUT I ENJOYED THE TRIP VERY,VERY MUCH, DESPITE…..