I found this link
which leads to my question:
Is the Reface MIDI cable the same as the MIDI cable that is used for the Tenori-On, and also the old SW1000XG used it?
If so the info from that blog is good DIY info if a replacement MIDI cable for the Reface is hard to find.
Or to construct a Reface-to-Reface direct minimidi-to-minimidi cable, or a mini-midi to male-MIDI-IN + male-MIDI-OUT cable.
All these options don't exist yet but could be interesting.