What about using something like this: http://www.amazon.com/RADTriage-2-0-.../dp/B002PIR1I4

No way can that be mistaken for a bomb or weapon and it should be relatively easy to read (they say to look at it under fluorescent light...do they mean UV/blacklight or will ceiling-tube/CFL fluorescents do the trick?)

Also, you could slip it into a credit-card pouch, between other cards to hide it, and act like you just forgot the pouch in your pocket after you took your wallet out. Once they detect it in the scan, the card will already have picked up the radiation.

Of course, the major downside is that once you know how much radiation you've sucked up, it's too late. The upside is that TSOs are, in all likelihood, sucking up way more than that from standing next to the Chertoffomizers all day.