I would be careful with any abrasive polish. My lightbar and the top which you mention was replaced due to pitting at delivery… I would assume it is painted plastic not metal.
If it is plastic or coated with plastic, plastic cleaner would be the best bet. If there is a scratch and it's painted plastic, polishing would make it worse but if it's a coating of clear plastic it may help. I've used these products on acrylic with success.
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