ID Turning a watch crystal?

SO I have a broken crystal on this old Movado. Here is a picture of the case:

The crystal goes over the 'faux' tension ring there, and there is a bezel that clamps it into place. The OD of the crystal is 31.6mm, which fits 'nicely' in the bezel (with just a touch of clamping?).

When it arrived to me, the crystal was broken off, but I could see that there was a ring of plastic clamped between the 'faux' tension ring and the crystal.

However, here's my problem: Every crystal I have/have bought that is 31.6mm OD, doesn't match the ID (which is 30.2mm). It is either too thick (for non-tension ring crystals) or too thin (tension ring crystals tend to have a much thinner wall).

SO, what do I do? My only thought is to take one with too thick of a wall, and put it in my lathe to turn it down. Has anyone done something like that? What sort of work-holding could I use for something like that? I have a sizable lathe/can make something, I just can't envision what it would be.

Alternatively, anyone know where I can buy watch crystals by both ID AND OD?

I haven't, but I don't see anything like what I'm looking for on their site unless I'm missing something? But at $300, thats about what the watch is worth 😁

I have plans for a single shot injection mold press. Fairly simple. The heating element uses a cartage heater, and thermostat feedback loop not unlike a 3D printer. The difficulty would be making the mold or die, which would need to have a nearly perfect finish. That could be turned on a lathe and polished, not unlike the cup and snap lid which are the first project to make.

If I did not have enough projects to keep me busy for at least 500 years, I would probably try it myself. A few prompts into AI (do not forget to tell it to turn off zero shot hallucinations.) And AI would be happy to design such a machine for you. Even do the thermal flow analysis for the syringe pump using clear shredded drinking water bottles. Might even be 20 percent correct. And if it does show the crucible shaped like a tea kettle, it got something right. The old guys and gals were doing this on the kitchen hob.

The other thing (I did not try it.) is AI might also suggest catalytic casting in the mold. I was going to try surfboard resin as it is UV resistant, but it was never in stock at TAP plastics using an RTV mold or mold liner. I hate ordering online.

Ironically AI probably is not too good at looking at fragments of watch crystal indexes. Most likely finding the most popular crystals with the largest number of instances uploaded to the web over the last 40 or so years. That is a statistical map, and we know there are "lies, damn likes and statistics."

IS there a good way to try other than ordering a handful? I've actually ordered quite a few of the others already trying to see if i could get lucky D:

Thanks! That's about what I needed to hear 😁 I might give that a try!