Hi,
One thing that works on older plastics, particularly clear plastics is to
clean them well and then use a blow torch to make them clear again.
This works well on pinball ramps (other hobby) but you must be careful when
heating or you will burn the plastic.
Light the tourch and move it quickly around the area to clear. KEEP IT
MOVING, if not it will burn and distort.

I hope this helps you a bit.
Practice first on an old piece of plastic. then once you have mastered the
process do it on your actual lens.

Novus #2 or #3 (for heavily scratched platics) to clean.

Ed