Depending on how deep the scratch is, you could try ultra-fine polishing pads or cloths to buff out the scratches. You can get a set of micro mesh sanding pads with a dozen or so pads are graded from 1500 to 12000 roughness.They use their own scale, but 1500 is roughly 800 grit, from memory. Scale model makers use them to buff out scratches or crazes in clear parts and restore transparency.

You should be able to find a video on YouTube if you search for something along those lines but the basic procedure is to start with a coarse grade then get progressively finer, buffing out all the scratches from the previous grade. It will look bad at first but should get progressively better - just keep a light touch and be careful not to sand through the paint. Finally buff it with some plastic polish and a soft cloth. Novus #2 is often recommended but I think it's an American brand so I don't know how easy it is to get here. I'd be surprised if there wasn't an Australian equivalent.