Autodesk hasn't put up the 2011 KOP yet, but they have the 2010 one up on
http://students.autodesk.com/?nd=kitofparts_view still.
Otherwise check out 1323's CAD library
http://team1323.com/cad/pages/sprockets.html though I am not sure any of these are the correct type.
3dcontentcentral is another good place to look for models but unfortunately gates isn't a supplier of CAD models to them.