A good friend of mine is a graphic design student, and he's made a run of about 50 shirts in black and white. They are printed on organic cotton American Apparel unisex tee's.
His 'one planet' design has been bought by several European companies for wall panels, iPad, and iPhone cases as well, but he's hoping to get his designs out in the clothing market.
The shirts are 27$ each, CND. Requests for shirts can be made through myself here, or on his website at:
Here's photos of myself wearing one. I'm 5'11'' and I wear a medium.