For all you year round riders (why wouldn't you?).
When I had my GT I made a pair of these...
I've probably still got the CAD file somewhere. Be easy enough to print it off and cut some by hand, just use a hot air gun to form it.
I used some 3mm of this stuff...
http://www.cutplasticsheeting.co.uk/clear-acrylic-sheeting/Clear-impact-acrylic.htmlI also used some 4mm to make this clip on screen cover for my GS when I do BloodBike duty. Although more often than not I use one of the group bikes.