Activity books with special pen that reveals invisible print?

[american_mama]

I am looking for an activity book for my 6 year old that involves mazes, word scrambles, and "invisible" ink which is revealed when you use the enclosed pen. It can have any or all of these; I just want it to be mostly a fun activity book and not so academic. I saw some at Target, but they were all for 3 year old's and basically involved scribbling with the magic pen across a picture, which then magically turned colors in exactly the right places. Very non-creative.

I have seen other children with activity books like this, but don't know where they came from.

[hellokitty]

Kohl's, Dollar General and Burlington Coat factory all have these books. We have a couple of them. They are good for entertaining kids while you are waiting for your meal at restaurants or on a trip. Dollar general has the best price, $2 each.

[californiagirl]

http://www.leemagicpen.com/

appears to be the ultimate source for these things.