With a lot of patience, the old ones can be re-used WHOLE.
(A talented person could make new ones from regular steel rivets.)
Pop the centers out the bottom through the rivet holes with a new pop-rivet or punch.
From the back side, squeeze the rivets with pliers until they are small enough to go through the holes in the pad. They are steel, so it's not easy. You'll probably have to push them through the pad with a punch. They will likely stay on the VIN tag. Squeeze a little more so that they come out of the tag easily.
Squeeze a little more so that they'll pass through the tag and new pad easily. You could leave them in the tag if they go through the new pad OK.
Take the "nail" out of a new rivet and slide it up through the old one. The old rivet center hole might be tight now, so you might have to tap it through with a small hammer.
Install the old rivet just like a new one using a rivet gun. *
POP*
Done.
Did I mention the need for a LOT of patience?
I believe it IS illegal to sell rosette-head rivets in Michigan. Ask Hank. Other states have various laws concerning these rivets and VIN tags. As a general rule, as long as you're handling these items for use in your own vehicle (I.E. pad replacement), you should be OK.
