A corner in my gutter is leaking because one of the rivets joining two
section failed, opening a gap at the bottom of the corner where two sections
meet.

I removed the rivet and temporarily put in a screw and nut (screw diameter
about 1.5mm) and sealant. I say temporary because the screw is a steel
screw. It will rust/rot away.

The original rivet is solid (no hole in middle). I googled for rivet
squeezer and it seems like the "C" openings on the rivet tool are not large
enough to work on a rivet at the bottom of a gutter.

A pop rivet would work but it would have a hole that water can leak through.
What is the correct fastener to use?