Here are some operators that I would not hesitate to use for a Buffalo Safari if I have not already;
Pro Safaris in their Lower Zambezi area.
Charlton & McCallum Safaris of Dande Safari area, Zimbabwe.
Chifuti Safaris Lower Zambezi valley, Zimbabwe.
Rodger Whittall in Lower Zambezi.
Buffalo Range Safaris at one of their Vic Falls areas.
www.kambakosafaris.com at the Niassa Reserve Mozambique north.
"ABC" African Bush Company (Jonathan Taylor) in the Selous Reserve of Tanzania.
"Luwire Safaris" Derek Littleton, North Mozambique.
"Luabezi Safaris" Jamie Wilson, Northern Mozambique.

All these guys hunt areas that are unfenced wild areas with everything one expects on a proper Safari.
Good camps with light fly camps for trips "out". Good PG numbers along with BG such as Lion, Leopard, Hippo, Elephant and Crocks.

Coming in for landing at my favourite place;