I have THE answer. I use a product called PLEXUS. It was deigned for aircraft plastic windshields and is primarily used for motorcycle windshields.(bike owners are as picky as audiophiles about their babys) I have used this on any motorcycle plastic parts for years. IT IS THE BEST. I use it on my mirror finish JL Audio subwoofers.Sold at most motorcycle shops. Note I spay it on my turntable cover(25 year old table) and it looks as good as the day I bought it.
PLEXUS
PLEXUS