Thanks. I had seen that before; in looking it's not available in any channels yet (or at least ones I can find) but I reached out to Asrock.
This one: https://www.amazon.com/SFF-8639-Ada...ni+sas+hd&qid=1607617471&s=electronics&sr=1-3
is available though and for 9 bucks USD I think I'll give it a try for the hell of it. It appears to be straight passthrough so hopefully low chance of frying the m.2 slot vs. simply not working. I have a SFF-8643 breakout cable laying around too.