George Murphy has them:

Blower motor: This climate control system operates the blower continuously
whenever any button except OFF is pressed. Consequently, after 80-90,000
miles, or 5-6 years, the heater blower motor brushes usually wear down and
no longer make good contact with the commutator. This is generally
evidenced by a delay of several minutes before the blower starts or it
suddenly starts when you hit a bump or hit it with your hand. A new blower
can be expensive, so it's worthwhile to remove it and install new brushes.
The brushes are fairly soft and can't be purchased from Bosch. (Don't use
power tool brushes - they are too hard and will cut a groove in the
commutator.)
I have a manufacturer who custom makes the correct motor brushes to fit
contact me at 423-482-9175 (voice or FAX) - I have them in stock.