You can also get them from
http://www.smoothturning.com, they have them for $8.99, with discounts for half and full case purchases. They also sell a cocktail shaker which is very similar in design. Not sure if WC sells that version.
Great job on the mug, hope my first one comes out looking like that! I just won one of these kits, so I'll get a chance here soon to try one out. I too like the foot detail you gave it. What finish did you use, and is the wood removable for cleaning?