Occasionally I have to repair the plastic body work on ATVs and snowmobiles. In this case I had a cracked fender and a broken headlight mount.
Here is one of the broken headlight tabs. Most of this plastic body work is impossible to glue. It can be welded but that requires special equipment that most people don't have.
I have found that the best way to fix these problems is by stitching the parts back together with wire. I drill a series of small holes and lace the parts up with stainless steel "safety" wire. McMaster Carr has a large selection of stainless wire, I think that the wire I used here is .025".
Here is the repaired fender around the head light. Notice that the wire is passed through each hole twice, this will hold the parts together more secure than a single wrap.