I had shocking polycarbonate round headlights on a w203. They were yellow and pitted with stone chips, and generally couldn't be seen through.
Removed the light from the car (because it's relatively easy to get the bumper off and do a good job).
Sanded the headlight with 600 grit wet and dry (with water) until all yellow and all large scratched and chips removed (don't need to polish afterwards).
Sprayed the headlight with a 2k clearcoat that you can buy in an aerosol (I think about £20 of Amazon or the bay of dreams). The cans have a push-pin in the bottom to release the hardener, so you have to use it immediately.
The clearcoat flows and fills in all the minor scuffs, and looks totally clean and see-through after spraying.
Is this an option?