Parts you will need:
- Some solder
- 3D printed replacement bracket:
Remove the two screws at the bottom of the joystick to remove the lower and upper outer casing. Make sure the wires are still OK by checking the continuity on both red wires leading to the top button.
Remove the two screws holding the top button down at the top of the stick. Pull the switch assembly out carefully - make sure there is enough free / untangled red wire to feed from the bottom of the stick.
The bottom part of the switch is clipped to the top part. Unclip the two and separate. Be careful not to lose the spring inside. The gold leaf contact is usually what has broken and has caused the switch to fail - as was the case here.
3D print the replacement bracket. Some light filing may be necessary to smoothen out the part.
Desolder the two red wires from the bottom part of the switch.
Solder on the new B3F switch.
Clip the bottom part of the new B3F switch to the top part of the original switch. Take care to sandwich the spring between the top part's white plastic shroud, and the bottom part's B3F button surface.
This hopefully gives a close approximation to the springy feel of the original switch.
Reinsert the button assembly into the stick, reinstall the top cover, and reassemble the outer enclosure.
A keyswitch might be a more straightforward replacement for this; will try it someday.