Excellent work, bengi3!
Polarising film is quite expensive, but I reckon a source of a huge sheet of it would be in a relatively late model LCD TV. I recently took apart a Phillips 55" LCD TV - now fixed - but one of the layers was a huge loose fitted sheet of polarising film. Needless to say, it might be the wrong type, but keep in mind if you come across a junker/cracked TV to scavenge for parts.
I recently took apart a PB100 LCD which I thought was part of the "syndrome" (in this case it appeared to be a kind of fungal/purple mold); however the LCD liquid itself had slightly leeched out underneath the polarising film - near where the trackball is so assume years of mild pressure has damaged it with the lid closed. Once the film was removed, it was clear the "purple mold" was the LCD layer itself. Unfixable.