I have repaired all kinds of plastic no matter what type it is, especially the old stuff, by taking a soldering iron and gently melting wire the size of paper clips into the plastic. It is a little tedious to do, but it does strengthen everything good. Support both sides, lay the bent wire on the plastic, then take the soldering iron and press the wire into the plastic, which will heat the wire and bury the wire into the plastic, smooth the plastic over the top for appearance. Not real clean, but at least the part remains in place. I have done this on plastic grilles and interior parts for years.