I lost the 13-tooth cog from my 12-23 nine speed Ultegra Shimano cassette. Does anyone have any extra nine speed cogs? Or a whole nine speed Shimano cassette? Ultegra, 105, or Tiagra groups in nine speed I think are all compatible. I just do not want to buy a whole other cassette for one cog. Email or PM me and we can talk price.