This is a long shot but...

I just got a Giant-sized Bandai Kamen Rider Cobra villain...

He is missing 1 arm.

His other arm is broken.

The flash around the arm where you insert the arm into the hole is broken. So I have two pieces- flash + arm. I can see that someone tried to glue the flash but that's pretty useless.

This there a chemical that I might try melting the flash back on the arm?

Or does anybody have any broken giant sized figures or removable mask giant sized figures missing the masks?

Maybe looking on Yahoo Japan for another broken one (or massive amounts of writing) might be the trick...

Any suggestions?

For the broken arm, you might want to try glue again. See how much of the existing glue you can remove, and try Zap-A-Gap. I've pulled off some great repairs on vinyls with it.

For the rest of the parts, yeah, watching Yahoo Japan might yield something usable. Good luck.