A replacement stem for a kids size glasses. Not at all universal but it does fit at least 2 pairs of glasses my kids wear. It's by no means a permanent or durable solution but it will keep the glasses on their face for a few days (or weeks if they're careful with them) while the replacement is in the mail.
Print with support, and you'll want to smooth out the layer lines on the part that contacts the side of the head or it'll tangle in the hair.
I found that I needed to gently chamfer the open hole for the screw to fit well. I also think even a well printed part will need a little fine tuning or sanding to make the hinge close smoothly.
To install, you'll completely remove the broken stem and then you'll need an extra long glasses screw that will go through the full width of the plastic and the hinge, and then threads into the plastic on the other side.