Honestly I don’t think we should change Rey’s lightsaber. It’s pretty clear that the prongs just cover the emitter and as she turns the gear it opens allowing the blade to ignite. That’s why her igniting takes an extra second compared to other sabers we’ve seen. The blade doesn’t push the prongs, but they open as the gear turns.
The prongs don’t touch the blade at all so there’s no need for them to be made of Beskar or Unobtainium