As an aside, I have seen (here on the Forum?) some time ago a few photos of someone's project where he added - using epoxy, built up - 2 more lobes to the cam of a steamer, giving a proper 4-chuff. If you can get to it well enough, it seems like a reasonable thing.
Durable? Not sure - epoxy is pretty hard, and a micro-switch spring typically resists little.
You know - would a 4-lobe cam have been too much to ask?