My book publisher, teNeues, produced this nice boxed set of note cards with reproductions of my post-it note drawings. The whole thing turned out beautifully; the drawings reproduced really well. I gave a box to my in-laws, and they use the "H is for Holy Crap" card regularly as a birthday greeting to great effect.

You can get them at places like Amazon, directly from the publisher, and other outlets. Let me know in the comments if you've spotted them in other shops.