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?
I saw the same "Kit" at Royal Farm store (Regional version of 7-11). I think it was $3.49 with discount coffee refills -- until you turn off the plastic outer layer to replace with wood.
I belong to a woodturning club and one of the guys did a demo on making the Coffee Mugs. I did a little tape on the project take a look at the link below.