Any tips for polishing plastic dial covers?

[Notimetolooz]

You may have to replace it. This place doesn't seem to have one for your model, but they might make one for you. I suppose you would have to send them your original. These replacements are made from a thinner plastic sheet that is vacuum molded.
https://dialcover.com/jmpalm/Inventory.htm

Or, if you want to you can do it yourself. I think there are a thread or two about making your own dial cover on this forum or on the Antique Radio Forum.