I have a quartet of nice pin punches with hardened pins in various diameters. I managed to drop the smallest punch, didn’t get my foot under it in time, it struck sparks from the concrete floor when it hit, and the pin snapped.
Not being able to replicate the pin’s neat mushroom head, I contented myself by chopping off a length of music wire and grinding the ends flat. Annealed one end over the kitchen stove, whacked it with another punch to get a flat, and it’s all good.
The music wire isn’t quite perfectly straight, but you don’t beat on things with a 40-mil punch, anyway.