I also considered a rubber roller and took wahoonc's of a rubber foot. I picked up a pack of 4, 5/8" rubber tips for $2.79. The drive roller on my dynamo is 19.7mm diameter, so the 7/8" rubber feet would have been too large. Anyway, the rubber tips were too long, so I cut it short with a razor knife. I intended to use the closed end but it was really difficult to install, so I used the other piece, it is basically a rubber ring. With a little spit as a lubricant, it slid on without too much trouble. In a test run around the neighborhood, it worked flawlessly. I'm not sure how it'll work during a longer ride, but I can keep you posted.