I might know something but it requires some elbow grease and most likely you won't get these sheets unscathed. These sheets are extremely fragile and even the lightest touch seems to scratch them. Furthermore the top most one (I think it is some kind of fresnel/diffuser sheet) is easily scorched as you mentioned. What you can do is buy an LCD assembly for a different MacBook (e.g. MacBook 1342) on eBay and remove the black tape at the edge. Carefully lift the LCD and there should be a bunch of sheets behind there. I suppose you could use these as source. You'll need to cut them though which is the reason why I say you will most likely not get it unscathed, but yeah, I believe poorly cut diffuser is better than one that is scorched and doesn't fit well. I'm just trying to figure out how you would want to cut it properly though to minimize the scratches.