I snapped a tooth off an encoder wheel last night and I'm too impatient to order a new one so I just made one to print out. I just freehanded it in photoshop based upon a scan of the broken wheel, so it might not be precision centered, ect. but I printed it out, put it in my drill and it spins really nice so it can't be THAT off. I've enclosed the source photshop document as well as the finished stl.