http://www.kanguru.com/fireflash.html
These are pretty old, but they do exist. I've read over and over again how Pro-Tools doesn't like USB Flash Drives. I was thinking of picking up a Micro and though that in theory, this would make a lovely portable set up. A MBox Micro Thumb Dongle + A Firewire Thumb Drive. They come in capacities up to 8GB!