Pretty much follows the image from the initial blog site.
I have now built 2,
one using a Sharpie Accent pen body

and one using a Bic Ultra Round Stick Grip

from radio shack i got the rest
Infrared LED
part: 276-143

Momentary Switch
part: 275-1571

1 AA battery holder
part: 270-401

here is a picture of the two i got so far. they work but are less than pretty.
the first one was the bic pen. i got the momentary switch before realizing that the switch was longer than the pen. thats one reason i switched to the sharpie.
the other thing on my pens is if you look at where the LED is, there is the clear cap on the bic and the end cap from the bic is on the sharpie. when i used the tracking box from the wiilib example, it makes it show up so much better.
Also i tried to find a different battery container that is just a cap for a single AA but i could not so i will have to make one later. When i get one, the battery on the sharpie will be inside with the original cap on the end.

also on the bic i initially superglued the button in place then the pen stopped working properly come to find out the glue i used is conductive (future glue) so be weary of that... heh
they dont look great but they work. so thats all i need. heh.