Gears and connections for Parallax servo motors

I'm trying to get into the robotics side of using my arduino but I don't know where to get the gears, shafts, etc associated with building robotic mechanisms. My first project will involve a Parallax continuous rotation servo motor. Do you have any reliable sites for procuring connections to the aforementioned servo? I have searched a bit on google but I don't want to invest money on parts I can't trust.
Thanks

The Robot MarketPlace has many parts you need. If you really need that special gear or pulley, use Catalog | Designatronics Store | Stock Drive Products/Sterling Instrument. Pricey but they have all the mechanical products.

Thanks for the suggestions!

Do you have any reliable sites for procuring connections to the aforementioned servo?

Hot glue can make strong but removable attachment to servo horns.