African Firm Surveys oon
There now exist various African panel survey data sets with firm data many of which have been collected by the Regional Program on Enteprise Development or as Investment Climate Assessment.
The Centre for African Economies has also compiled comparative firm-level data for the manufacturing sector, covering Cameroon, Ghana, Kenya, Zambia and Zimbabwe. This data can be downloaded from here.
More African enteprise data sets can be downloaded from the World Bank/IFC. Doing so requires registration.