Try Tech-Steel works great i keep in my tackle box... 2 part epoxy putty.sticks to anything.
but try replacing the rivets it's not very hard... 24rivets = 2 beer
then wash it down with "gun wash" or silicone remover let dry and apply a roll on bedliner for trucks
problem solved! I did it on my 12 footer last spring has'nt leaked yet..
Tech Steel available @ Benson Auto Parts ,, Auto Parts Extra ,, or any automotive place.
but do use the Beartex scuff pads the grey ones before applying any sealant for proper adhesion
if you do go the Rivet route seal it anyway.
Randy...Muskieman