I was looking at doing this as well. I have an original GBA and have been looking into swapping the original screen out for a backlit one.
In researching this on the web, it looks like most people swap the original GBA screen with one from a GBA SP AGS-101 model. I looked these up on ebay, but they seem to sell for $75-$100, which was a bit more that I was looking to spend for a mod like this.
I found the following on dx.comhttp://dx.com/p/gb-station-light-game-c ... idge-29726
Looks to be a knock of of a GBA SP. Has anyone used one of these for any projects, or know if this would work to do a screen swap?