One of the leather strap anchors on Mary’s giant haul-everything-to-a-concert(*) handbag pulled its rivet through the canvas fabric:

We knotted the strap around the zippered opening and completed the mission.
Of course, it wouldn’t have pulled through if they’d splurged on washers, but noooo too expensive:

Some rummaging produced a pan-head M3 screw of suitable length:

A slightly battered acorn nut was a special treat for the inside, with another washer to keep me happy:

That was easy!
(*) At Tanglewood, where they don’t strip-search you on the way in, tow-behind coolers seemed de rigueur, and a good time was had by all.
Ah, the B.S.O. in the Berkshires on a balmy summer night. What a special place Tanglewood is.