I do not see why not. If you cut out the middle of a 2 liter bottle, that would probably give you enough material. Just cut around the top and bottom and then make a vertical cut. You could use a heat gun to shape the plastic into a visor shape and then cut to fit like any other visor. This would yield a clear visor, of course. You could use that VHT Nite-Shades paint to get a black tinted visor though. I have also read about people using Krylon X-Metals paint to get other colored visors.
@adam4472 Lowes, Home Depot, Sears, and various other hardware stores should carry them. Check Walmart too, they might
@dajdog1 The method is probably pretty similiar to the method used in the thread i posted above with the exception of using a heat gun to soften the plastic enough so that you can remove/ reduce its tendency to curl. I'd also add a step about using superglue to glue the pieces together.