Not sure if I can help you out or not but please try contact L.David Keith at Grey Ghost Safaris.
He is a long time booking agent (and a good friend of mine) and I might be thinking that an outfitter that he represents from the Eastern Cape may have some of these, or they may be the Sth American variety, not sure.
I don't have L.D.K's contact details with me but can find them for you if you need. You can p.m me for contact details if you wish.
Not sure if i'm 100% accurate with my advice but it's worth a try.
I hunted with Simon Kyle Little of Australian Big Game Safaris in the Northern Territories. I will recommend him without reservation. He is a true hunter. There is a nice wind that kicks up as a sea breeze about 10 AM everyday. I shot a bull at 18 yds with him. I went on a management hunt and ended up negotiating for 3 bulls. I shot one with my bow, one with his double and a monster with his .375 that tried to kill us. What an awesome trip. I used Easton dangerous game arrows and Ashby 325 gr 2 blade broad heads with a 80lb hoyt Vectrix. I Shot one bull and 3 cows, all complete pass throughs with this combo. My buddy shot one bull and 2 cows with same broad head, 80lb bowtech. same result