That is an easy fix. If you have a dremel or other rotary tool you can use a small buffing wheel with plastic compound to smooth off the crusty coating, then plastic polish to buff it smooth, then some Krylon Fusion plastic paint to restore it (the Krylon bonds VERY well without primer to these plastics)
Oh, wait, looking closer it looks like yours might be missing some ridges underneath, broken? Never mind. Go to a motorcycle salvage yard and you may just see one very close in size on a lot of bikes, chances are, they are the same underneath and will fit. (I mean, they LOOK kind of universal, right?) Maybe the manufacturers all sourced the same supplier? Worth a shot.
Palm Beach Gardens, FL
amateur photographer, hot rodder, motorcyclist, adventurer
"Four wheels move the body. Two wheels move the soul."