Have you tried going to a sign shop and see if they have any plastic signs that they replaced?
I've found that my 3 local shops say they can't reuse that plastic, and they just trash them, so, every now and then I go by and ask them what they have going into the trash. I often score and have some neat plastic to fool around with in my workshop.
Here's the signs that were on my wife's business, they are 1/4" white plastic with the blue vinyl held on with an adhesive. After 10 years in business, it was still easy to peel off the blue vinyl, so I could have the white plastic to use as I wanted when she closed the business down in 2007.
Here's my camper air fairing project... I had a large 5" gap between the underneath of the overhead cab section of the camper and the top of my truck cab, and was told by Marty at ATC that I should make something to deflect the wind from hitting the flat front of the camper under the overhead cab section.
Searched on how to bend plastic on the internet, got the Nychrome heating element (like what is in an electric heater), built a jig, and made what you see above.
I hope to make some storage behind the plastic air fairing... someday. Brackets attached to the front of the camper, maybe holding some extra water, or chairs, or fishing equipment or something. Several WTW'ers have done the same thing.
As my overhead cab section of the camper comes out right to the front of the top of the windshield, I haven't figured out if and/or how I'll make a wind fairing for the flat front of the overhead section. I do like the photos that Ski posted, though.
Not sure I'll do anything as I'm getting pretty good gas mileage with my 4.0L V6.
Photo of my ScanGuage II.
Average is 20.5 mpg, and going flat to slightly downhill 24.7 mpg and just a little coasting when I took the photo below.
172 is my water temp and 141 is my trans fluid temp.
I do drive a bit on the low side, usually around 60 mph