James
If the C40010 is the right number then Aircraft Spruce has them for $49.50.
http://www.aircraftspruce.com/catalo...clickkey=53010
The new number is RAB40012 made by Rapco. But based on Rapco's chart this is for a Cessna 340.
http://www.aviaquip.com.au/pdf/rapco/brushes.pdf
The Rapco chart calls for a RA1306 or RA1543 for a Cessna 337
I have been out of the country for the last 10 days, didn't see your question