I hunted with Threeways Safaris in Zimbabwe in 2012 with my father. Their main buffalo concession is located just across the river from Kruger and we each took very nice buffalo and had a great time during a 12 day hunt. Last I heard, their typical buffalo hunt is 10 days.
http://www.threewayssafaris.com/If they can't accommodate you, or if your heart isn't set on a Zimbabwe hunt, my place in South Africa is offering a 7x day buffalo hunt package for $13,000. The hunting area is also located just outside of Kruger and clients take some great buffalo there each year. Our success rate is very high.
http://biggamehuntingadventures.com/packages/If you would like more details on either place, don't hesitate to PM me.
