I recently saw a thread in another forum that looked interesting. I'm not sure I would use it in a high-stress area like mounting screw tabs, but it's worth mentioning for the cosmetic repairs. You can find a used/broken piece of plastic from the same or similar car. Find a part that matches the color. Break off pieces of plastic and dissolve in acetone, till you get a paste-like consistency. Put it where you want it and it will set back up to a hard plastic. This only works for abs plastic, I believe.
You may be able to use this with another method. Possibly use a piece of stainless mesh/screen and build up the acetone/abs mix to adhere it to the part. It wouldn't be hard to experiment before trying it on the part in question.