I spent way too much time trying to figure out why the lid was broken, turns out the entire plastic assembly inside became disconnected from the metal casing, not just the top of it. So, yeah, the screw part is plastic, not metal.
I thought then that I could just remove the metal casing to fix it, but during the process of trying to remove the casing with a pair of "long nosed vice grips" aka pliers, I luckily crimped the side sufficiently to lock the metal casing in place with the plastic threading. So, voila, repaired.
I'm not sure if it counts as serendipity. I mean, I did try to get a repaired lid, but not a repaired lid in this fashion. Maybe the Persian Princesses of Serendip would know. Have a good one.