@alexonit I just checked my local hardware store next town and 4mm brass rod is the closest I find.

Okay, they are also offering 2.8x25mm copper nails. Which I actually do have a single one here. :-)

My hardware collection also includes a few brass-like looking screws that I could repurpose into rivets. But I reckon I have to upgrade my burner first. I'm not a metal worker by any means, so I could be totally wrong, but I imagine that some heat is necessary to loosen the work-hardening effect when beating on them. I will do some experiments on Saturday and report back.