Somebody on this site made a small fairing for his motorbike from a rear fender from an mx motorcycle. He said it worked well and gave him a few extra mph. It looked good because it wasn't too large and he cut out a hole and mounted a headlight in it.
Nice! I was thinking the same thing the other day, but I figured that the other motorist wouldn't appretiate me tacking to get back up wind on my way home!