While I have never hunted NAM, I don't disagree with anything Flags said. I killed everything NAM has to offer in RSA (or elsewhere) except Dik-Dik (DG excluded). Well, I do have a Dik Dik that is the same except for SCI....The RSA Kalahari has excellent native Gemsbok. I just somehow never got there (NAM) probably because Black Wildebeeste and Nyala and some tiny ones available in RSA only were on my priority list.
You might consider checking with reputable Booking Agents like email@example.com or Atchesons
The recommendation Ramhunter made is also very good.
BTW, you can get Mountain-Hartmanns-Zebra in RSA....and NAM does not have Cape Bushbuck, Cape Kudu, Oribi, Val Rhebok, Red Duiker, Blue Duiker, Sunni, etc that are all indigenous to RSA