My A/C blower has had the "tap & run" thing going for about a month now. So I took it apart today and pulled the brushes out and replaced them with new ones I found at ACE Hardware for around $3 each. Easy job to do, bend the little tabs that hold the brushes up with a small screwdriver, cut the wire leading to the old brush, pull out. Take to store and find the same size as close as possible and put back in. Bend tabs back into place, twist new wires to old wires and solder into place. Oil the thing while you have it out and reinstall. Job took about 30 minutes not including finding the brushes.
Motor runs great and no more tapping to start it
On another note, NAPA has GM brushes that are the exact size but are to long by a good 1/2 inch, also were not in stock. You could file them down if needed. The brush size from the motor I took apart was M-41