That was one of the switches I found where I wondered how long it would take for anyone to find one in a keyboard (mine was NOS from STRONIC in France, but I also have some used examples from Bulgaria). There's a few still waiting to be found in a real piece of equipment, in particular Tokai SPT-0101 (opto-electronic with Alps mount; only seen on the Tokai website) and GRI KBR (looks similar to Futaba MD series but is a reed switch; found the Futaba patent, but it has never been seen). I had real doubts about the silly little Stackpole switches (series name not known, but we have the patents), but snuci found a whole keyboard of those, including an unexpected alternate action version.