Are you only looking on the Durango site for these ? If so try looking as others have said to JE Models or MB Models. Both have a fairly extensive stock of parts for all cars, and are generally well stocked. They also carry upgrade parts such as RW (for your spur gear) and Tresrey/Exotek for the other bits.
Give them a try
www.jemodels.com
http://www.rccarshop.co.uk/index.php/ < thats MB Models