Re: STEREO A/B/Y switch ?
I know nothing of the brand (they do have a website as well)...but the description seems to match your application*
https://reverb.com/item/28215482-saturn ... californiaI'd suggest giving them a shout
there is the t-rex
https://www.t-rex-effects.com/polyswitch/BUT it appears to be only AB (no Y) and completely passive
Our fine friends in the keyboard (as opposed to the guitar) community may be of help as it probably matchesd their use models more
Also you may want to run it by tech support at radial or some of the other manufacturers
probably if you specify 2-in/4-out or speak of routing stereo-PAIRS that might be helpfu. Maybe say "to PA" or "to stereo PA" or even just "stereo outs" instead of "amp" bc of what people sort of assume (amp=guitar amp=mono)
--though figures always help with routing
*If I am understanding it correctly -- thanks DavidWS for doing the legwork on the figures