I have found these, based on this reddit thread.

- CTS Electronic model 251B12T104A2NB
- These have a 12mm shaft though the original has only a 7mm shaft. [EDIT: I measured the original wrong, they actually both have the same shaft length]
- However their "Throw", the lock-to-lock sensitivity, is a hair "short" of the actual joystick extremes, compared to the original, when viewed in the joystick control panel software. One might be able to overcome this by setting the joystick sensitivity up a hair in the game.

I've soldered a couple in, and I'm going to try them out in-game when I get a chance.