Just for reference, that's a drive screw, not a rivet. You can buy them new from McMaster or other places. Used to hold nameplates on a lot of older machinery.
Learned this today. If you start turning that glan nut. Listen for a click sound. That is the end of the clip you want to start out of the hole. Other end shouldnt make a sound as it goes past slot if both end click spring clip is broken. Lol
Ha! Thats how I felt the first time I saw it done. Now with that said I once saw one so tight the guy had to use a 5ft pipe wrench. Good luck with your projects 👍