Short story, made a rivet from stainless rod. One end with shoulder, the other end with hole ( to make that end easier to flare).
Worked really well. But I think it’s unnecessary work. Both friend and I had the same idea of finding Chicago screws that will do the job. And those screws are out there.
Funny thing they are called M5 Chicago screws, but the actual screw portion is M3. Pictures show better. Oh and you’d have to trim the length a tad. Is brass hard wearing and strong enough? I think so.
Back to my rivet. Here’s a sequence of pics using another old wiper arm. First couple show how you can hold the “c” connector in a vise and pull back on the arm to release hub. Head of the stock rivet drilled out and punched thru. Stock rivet 50 microns larger diameter than the Chicago screw… yadda yadda yadda…you get the idea.