What should I be searching for?
 

Gauge glass or clear plastic covers?

There's a small scratch on the tach cover and dust in there.

A quick clean out and some Mequiars Plast-x polish would have it looking like new in no time.

^ this, if its badly scratched

Been testing the equivalent of your infamous Made in USA Novus 1-2-3 on acrylic here. The same material those gauges glasses are made of if not PC. The stuff fills small scratches and sort of disappear as it dry, or as you polish (few secs). Well that is what the Novus knock off I've been using does here anyway. Makes any acrylic glass looks even better than new. Scary chemical in fact.

and cheaper than Plastix :p

e.g. Novus Plastic Polish Scratch Remover Cleaner Kit 1 2 3 2oz Bottles 1 Each | eBay

This is great news. So I can take those rings off or the entire top cover to clean or dust in there?

BTW...this stuff works well on the vinyl back window too. Working on it about a month ago, got mine (now 13 years old) looking virtually transparent again. Gotta do the inside as well as outside.

Neat
 

THanks for this great info