I publish with Focus, Phoenix, Abantu and East African Educational Publishers.
EAEP are more likely to be interested in novels sooner than the rest; Phoenix will publish Children's readers faster than the rest, and Abantu directs authors on what they want. If it is adult fiction start with EAEP then FOCS, Phoenix in that order. Abantu are not into novels yet. Then there are others like Oxford, KLB, Mcmillan, Longhorn etc. but I have no experience with them.