Mending chinstrap loops on a Gallic G

[Gallic G]

Hopefully the pictures will turn up, but there really isn't much to show - the attachment has come away from the rivet, because the rivet has hardly splayed at all. I assume I have to get rid of the rivet, but it is still tight, so how to do that without damaging the decorative stud on the outside I don't know - pincers? I also need replacement rivets, but I've never done riveting before; happy to give it a go, but don't want to write the helmet off in the process.  From the way this is made, I'm guessing it's a rather common problem