Loc-tite was my first thought, but I don't think Loc-tite and plastic are compatible. Hopefully someone who knows will tell me I'm wrong.

I had to replace both power mirrors on my truck (one of the mirrors had cracked) and I was quite surprised at how lost cost an off-brand replacement was. They've worked fine for over two years. Still, if you can find something at a salvage yard - go for it.