Seeing some of the suggestions made by Dr. Ruderman, made me think of two books that might prove helpful:
Kate Lowe along with T.F. Earle have an edited volume, Black Africans in Renaissance Europe, New York: Cambridge University Press, 2005. There are a variety of essays that cover Italy, Spain, Portugal, and Britain (I'm sure there are more that just escape me). There is one essay, that talks about Alessandro de Medici, the "black Medici." There's another that discusses Isabella d'Este and her desire to acquire a black female child, essentially as an accessory.