Maybe something like this?
http://www.mec.ca/AST/ShopMEC/Electr...ro-charger.jsp
Notice the difference in size compared to those small ones - that's the other key. I had a small Solio solar charger, but it took probably 2 days to fully recharge its own battery, before it could put out enough juice to sustain charging even an iPod. (although the sun will be stronger in Africa, obviously)