Could maybe the re-released Copplestone Zanzibaris be used?
Yes.
He also had irregulars, easily represented by non-uniformed askari from the Darkest Africa range:
These Sudanese IBEAC troops in Uganda are survivors of Emin's garrison. The picture is from after he had parted company with them, but it gives an idea of how ragged and non-uniform they had got, following years without resupply. Some have replaced their white Egyptian-issue tunics with blue jerseys but many were in rags or home-made clothing of oxhide or local cotton. Worn-out fezzes were often replaced with straw hats decked out with feathers, or brimmed hats made of cloth. Such things as leopard-skin loin-cloths were also worn over their trousers by some individuals, and they had a habit of applying their own rank chevrons on a whim (as many as they felt like and regardless of their actual rank) to "big themselves up."
They were issued with new blue jerseys by the IBEAC, but this was to replace worn out ones, they did also wear such jerseys (and new dark blue puttees) while serving under Emin when their Egyptian uniforms started to wear out.