Does anyone know where i could buy plant food for my bonsai tree in or around basel?

Have you tried Jumbo? They have a wide selection for plants, not sure how specific they get. If they don't have it they might be able to send you in the right direction!
http://maps.google.com/maps?f=q&sour...8&z=16&iwloc=A

Thanks for the advice abzurich, Jumbo had exactly what i was looking for! :-)