Last night, I finished the rebuild of the pump and installed back on the car. Works great, no noise, and ready for another 250k miles.

There are a total of six bearings in the air pump:

Pulley/clutch bearing (1)
Air vane carrier rear cover bearing (1)
Air vane bearings (4)

Generally, it's the pulley housing bearing that causes the problem because it spins 100% of the time, and the rest of the bearings spin only when the clutch is engaged during engine warmup. I replaced the pulley bearing and the vane carrier rear cover bearing because it was fairly easy to service. The four small bearings on the air vanes (two bearings/vane) can be replaced, but great care must be used. Mine seemed perfectly serviceable, so I cleaned and greased them and left in situ.

Here are the product numbers for the bearings:

PULLEY BEARING
32BG05S18G-2DS (see weblinks earlier in thread for vendors)

VANE CARRIER REAR COVER BEARING
B188 (Timken 1 1/8" X 1 3/8" X 1/2" needle bearing)