Next release in my watchmaking tools is a 40mm "deep dish" crystal press die. This is a bit of an odd size and doesn't come in a lot of die packs. The deep dish deals better with very high vintage style crystals.
I make mine with PLA and have a lot of success, but you can make them out of any thermoplastic.
The mounting hole is 5.05mm for my press, but you can easily adjust this to whatever size.