Fixing them might not be as difficult as you think… Often it is just the reflective backing that has become darkened, and it is that which needs replacing.
Carefully peel off the reflective backing – it is this which has probably become blackened, due to sun exposure.
Clean the rear side of the LCD glass if required, with 99.99% iso-propyl alcohol
Replace with a piece cut from a silver foil roll
A tiny dab of glue may be required (especially if you have cleaned the rear side of the LCD glass with alcohol).