You might consider doing a technical stop (for fuel and customs) at Oranjemund, but prior permission is required from Namdeb. Than you fly direct to Cape Town. Alrernatively, you do a technical stop in Upington, and than fly direct to any airfield/airport in the RSA. Quite a lot of Nam's do that, as Cape Town is quite cumbersome if you're on a private flight. Consider landing at Stellenbosch or Fisantekraal after clearing at Upington.