peter is right, there are several things that will weld it(Methiline cloride, the PVC pipe glue. tetraclorethane(sorry, it's been 5 years I hope I got the name right, I moght not have)(anyway its the stuff that kydex sells to glue it)
but these only weld it.
Iknow of nothing that will give a trustable bond metal to plastic.
I think your best bet is a mechanical fastener.