You will need to ID the type of plastic you have.
See attached guide.
If it's polypropylene, you will need a special product. Nothing at your Home Center will work. Trust me.
The thing that will work is FUSOR 143 (Lord products).
This stuff is used to repair plastic bumper covers.
It's sold in small quantities by www.autobodystore.com
The minimum (kit) is around $60.
You may need to build a jig to hold everything in place while you apply the "glue" and to allow it to cure.
The Home Centers have a plastic primer that will permit the use of any (rattle can) paint.