I finally got around to building a shroud, out of fiberglass, for the replacement blower.
I opted to turn the blower 90 degrees inside the case: It sucks in air from the front, and blows it down at a 45 deg angle, free flow, so the shroud redirtects the airflow behind the motor.
Here's a pic of the foamcore assembly, used as a shape for the fiberglass:
Still runs fine at 5 volts, and "quiet enough".