Day 28 in The Beat Handbook: 100 Days of Kerouactions is titled, "On Clothing," and references the below passage from On The Road.
If you want to dress like Jack, this passage contains two big hints: 1) wool plaid shirt; and, 2) canvas rucksack. You've seen lots of pictures of Jack in his famous wool plaid shirt. Here's an example (definitely plaid, maybe wool).
I posted a picture of Jack's actual rucksack (below) with advice on where to get one on March 25, 2009.
One important point here (that I reinforce repeatedly in my book) is that the beat way to acquire such items is to scrounge for them, either as hand-me-downs or from a store that sells used clothing/items. It's better for the environment and cheaper on the wallet. And the items will already have a beat appearance.
Tomorrow: On generosity.