I have repaired that same damage(several times). Here's how I did it:
First, clean the bare stuff well with rubbing alcohol. Don't worry about the rough surface. the rougher the better.
Second, mix up some epoxy resin.
Third, paint the epoxy on the bare part of the broken bits with a small chip brush. Work it into the surface well.
Fourth, add a bit more on the surface of the fairing and set the broken part in place. You want the fairing sitting with the headlight pointing down so the broken bit doesn't slide around while the epoxy cures.
Last, let it cure for a couple days so the epoxy has a chance to get to full strength.