you should be able to get brushes for a dc motor. Seems like they have them at the big-box hardware stores. Or McMaster-Carr Not sure what you would use on the other side as a wiper. I suspect the Herse did this as a gimmick, it really doesn't sound like a particularly good idea to me. Especially if money is an issue. Motor design is fleeing brushes as fast as they can, and that's a much better application for brushes than a bike light.