If you can get your old bumper off how i described, then a GT/GTP bumper will fit. A junker is probably your best bet since they'll be painted. most new replacement body parts aren't painted.
You can try to get the moisture out and re seal them, I just dont know what sealant to use, perhaps someone else does.
You could also try tinting them and see if that covers it up.
The other option is a place like GMpartsdirect.com, they should have some for a fair-ish price considering they'd be new. If not, try the wrecker.