I would HIGHLY recommend Threeways Safaris in Zimbabwe. They have a concession just north of the river across from Kruger. Tokkie and Quinn are first class guys and will show you a lot of Buff and Elephant to choose from. Both are born and raised in Zimbabwe. They usually fill up a year ahead of time without even advertizing, with many repeat customers. My son and I went with them this past February and had a very successful hunt. I most definitely do not recommend February however. We had to take that time because of my sons time restrictions, but we had to contend with temps of well over 90F every day. (sometimes well over 90!)
We took two Buff, an Elephant, two Zebra, two Impala, and a Baboon on a 10 day hunt. I would highly recommend June thru August for the best weather.