I sanded down larger ones.
What I did was sand down ones which I purchased locally at a starter/alternator rebuilder shop ... I didn't ask what they fit. The worker just looked at the old one's shape an matched it with ones large enough that I could sandpaper them down to the exact size rectangle shape required.
The only difficulty making them was making the wire come off at exactly the right spot. I ground a little groove in the brushes top and Kwick J-B welded the wire into the groove and then it would come out at the right spot. From there , I soldered the leads onto the cut off old leads and oiled the motor bearing with laquer thinner mixed with moly wheel bearing CV joint grease.
The blower motor is running well. Also, I should tell you that I used a hobby grinder to shape the contact area, where brush touches the copper motor shaft, to "exactly" the same oval shape as the old worn brushes.
Motor has never been quieter and blows very well, even on the "off" position which revolves very slow at all times in order to keep cabin ventilation coming all the time. My draging bearing shaft had previously prevented the "idle motor-ventilation" function from even working.
TOTAL parts cost was $2.00 US dollars !! But I spent most of 2 days working on it. Oh well, I love to tinker with my MB anyway.
Luck to you, DanielW
PS If you decide to do your own write me back if you need step by step of what to remove to get the blower. It's buried under the wiper assembly ----- But you may know that if you know it needs brushes. DanielW