I've got a "saddlebag" style set from m-wave that was cheap and does well for everything but my laptop -- I'm seriously considering just picking up a set of hardware (hooks and a bungee from the hardware store?) and adapting one of the ubiquitous dell "messenger bags" for pannier duty... we have dozens of them just lying around... but really any messenger bag, even your Timbuk2, can be adapted into a pannier bag with a little effort, or you could make/buy a basket or bag that the timbuk2 fits inside of.