[cleveweld]

When I bought my car the upper portion of rear seat was no longer attached because 5 of the 8 rivets holding the hinges together had sheared off.
I found a company called Jay-Cee Sales & Rivet, Inc. They had the exact rivet I needed to repair my hinges. Rivets have a 1/2" dia. flat head, 3/4" long x 1/4" dia shaft. They are annealed (hardened).
I used a torch to head up the end of the rivet and then mushroomed the end with a hammer.
I had to buy 100 so I have a few extras if anyone needs some.

RIVETSINSTOCK.COM They have any rivet you might need.