I saw a guy in the DFW airport today wearing a shirt like this. I didn't get my camera out fast enough to get his picture, but at least I spotted it in the wild. You can find this shirt in black at MartialArtsmart.com, or in white at Acuwear.com. August 2, 2004.
By the way, the definition of "Qi", from acuwear.com:
Qi (chee), n. Matter on the verge of becoming energy; energy at the point of materializing. The essential energy of the universe which maintains the vital activities of life.