If you don't want to use a Zanzibari figure to represent him in native garb, his outfit when working for the Germans was a white tunic and trousers and a broad-brimmed hat. He was also heavily bearded. Nothing springs immediately to mind that could be used without converting, but maybe you can think of something.
But if you can find an explorer body that you like the look of, I have a spare head from the Warlord plastic Zulu War British infantry you can have. It is heavily-bearded and wears a broad-brimmed hat, conveniently enough. PM me if you are interested.
The fellow on the extreme left (photo courtesy of LAFer "Belgian").