A bit more information about the lamp that you are using and the mesh that comprises the "screen", please. I appreciate that it will be difficult to take photos that show what is wrong in your eyes about the lamp, but a few words might help. Some of the photographers here may be able to advise how to construct a reflector that might produce the effect you desire.

BTW, I have no qualms about this hack. Some Macs have to be sacrificed to maintain a supply of spares, and this one sounds like a prime example for donation rather than restoration.