Cut the post-it note into thin strips, stopping just before you get to the sticky part so it stays in one piece.
Wrap the Connected end of the post-it around the metal part of the pencil and wrap it in tape. It's okay of the tape looks wrinkly because you're going to cover it.
Wrap the first yellowish rubber band around the writing end of the pencil, then slide it down over the tape. Repeat with the colored one, then the other yellow.
Write with the black Sharpie all over the exposed pencil, especially on the Muggle company's words. Then use the envelope opener and scratch a good half of it off. It'll give it that I-just-used-this-to-win-the-world-cup look. Be sure to scratch off the Muggle words.
Using the envelope opener, etch in your favorite broom model toasted the post-it note side so you don't sharpen it off anytime soon.
Give it a good pinch like this to give it a just-ridden look.
Now ruffle your hair like James Potter and you can tell everyone you were playing Quidditch at work. =)