According to that eBay listing, the cover attaches with clips and Velcro. I'd be concerned with dust and grit getting between the plastic and the cover and sanding/scratching your plastic (same as with anything covering and contacting your plastic, like a fender bag).
I think your best bet is to put the word out that you're looking to swap your red plastic for green plastic, and hope that somebody with green plastic is looking for red plastic. Otherwise... save your money.

Greg