Got a replacement blower #ECM#motor from northamericahvac.com - had to order from the States. Installed it, and ... furnace was still throwing an #error code meaning "incorrect #signal from ECM motor" once, then "no signal from ECM motor" forever after.
After double-checking, I saw the part number on the box didn't match what I'd ordered - but that turned out to be a red herring. The box number was for the unprogrammed motor.