Sheldon Cooper Clothes <3 ?

Ok well, I heard The Big Bang Theory cast would be at Comic Con 2011 so I wanted to go as Sheldon Cooper cuz well, I love him, and he is just all around awesome!!! Well anywho.... I already have my own DC tshirts that I have had for a while, and the only thing I need help on is his pants and messenger bag... What type of pants does he wear? Like pattern .. also where can I find his messenger bag?