Short of lasering or arc welding the finding, you must disassemble
it to solder. Use a ball bur to remover the spread rivet on one side
at the lever and push the rivet out with a fine point center punch
or a dead bur thats been sanded to a point. remove the lever and
solder . Rerivet with 22ga., file it to a point if necessary to work
it through, 24ga will fit easily but is way too sloppy, the hinge
will drift too much.