[Christ]

Well, plastic makes life fairly easy.

Sand the area you want to cover down to bare plastic on the backsides, get yourself some sodey pop bottles, and cut pieces to install with plastic cement. (Modeling glue.)

If they're ABS, and you have any pieces of ABS laying around, you can use acetone to "weld" the pieces together. ABS plastic gets all mooshy in acetone, and once the acetone dries, the ABS hardens again.