There has _always_ been tube mic cable, right from the early days.
Seriously: the older multipattern tube mics (the type that have separate standalone power supplies, and allow selection of the pattern from the power supply rather than by switches on the mic body) have always needed multiconductor mic cable like this from the power supply to the mic itself.
You should have a shielded twisted pair for the audio, like any other mic, you should have a pair of fairly heavy-gauge wires for the tube's cathode heater supply, and you should have one or two light conductors for the bais voltages for the mic capsules and the plate supply for the tube stages. The pattern selection is accomplished by varying the bias supplies for the front and rear capsules.
It used to be that the only cable supplier to use for this was Gotham. Now, lots of suppliers are in on the act.
this isn't like tube mic stands, or tube splicing tape- this stuff actually does have a real purpose, and there are (very expensive) mics that need it.