Addendum: some additional searching shows a few interesting "trigger / gate addressable voltage" sources, none of which are solutions for the exact use case above, but all could fit in other somewhat similar use cases:
-- Random Source SEQ8 XL Serge Sequencer
-- SPUTNIK 5-STEP VOLTAGE SOURCE
-- Xodes PV44
(Capturing these here in case its of interest to anyone else.)
... all told, Verbos Sequence Selector (VSS) or a smaller HP/$ version of its selector function would be my best fit solution in this case. If you know of any great VSS alternatives, please let me know, thanks!