As others have said you could use Brasso or dura glit.
If the scratch is deep then cut it back using what is called "4 nought wire wool" its available on ebay and is used to polish car windscreens, it does not scratch glass, and I know the Eriba windows are perspex, macrolon, polycarbonate whatever but it does work. You will need to polish the area after cutting back and for that you can use use the Brasso or dura glit, I have also heard of people using toothpaste but have no experience of this
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