I have not found a way to bring back faded/browned out light covers,
tried putting them in bleach, no go!
I did find some locally, I painted the top(s) with red gloss nail polish.
You want your roll over buttons to move freely in the hole(s).
I also found, that if I adjusted the contacts under the roll overs
carefully, the ball(s) would roll over them nicely with out deflecting their
movement; i.e. the contacts just make contact with a slight/light press!
As far as the actual roll over buttons, I like the Yellow to be nice and glossy
as well as the Red!
Terry K

Trying putting the plastics that you want to turn white into a strong hydrogen peroxide. The stuff you buy at a drug store will work but it takes way longer. My friend got some from the university that was super strong.

We put everything in a clear container with a lid, filled it with the peroxide, and put it in the sun, shaking it every chance we got. After about a week all of the yellowed/browned plastics were super white. It made the old lane guides look basically the same as the new ones we purchased.

It worked really good on the gottlieb game, and worked fairly well on a Williams but I didn't leave them as long for the Williams.

I bought a parts game of similar vintage to my collection games. It has repaid me several times more than its purchase price. You can go to Joe Shope ( a very nice and fair collector) when you need a specific part, but you will do yourself a favor by having your own parts game. I'd check Craigslist in your area for a ~$100 game.

I have bought light covers sets off eBay twice in the last few years. Never thought of them as too rare.

This may help: https://bingo.cdyn.com/techno/parts.html