The spousal unit took my "dented" one off the machine and to Ace Hardware, where he found a rubber wutzit to replace it. Mrs. Boats is right. When the machine is "down" in the cabinet, you need to find something to keep the rubber off the wheel...that's what causes the dents.
ETA: If that fails, I got a new drive from Guy Baker, but it didn't have the bobbin winder pulley on it. It worked, but I wanted that pulley. Cost was $8...