T-shirts are made with Hanes Tagless T's. They are available in 3 sizes of small, medium and large, and just so you know, they are all a bit oversized and do not shrink much, so you may want to go with a smaller size.
The price is $22 which includes the shipping cost. If you live in Toronto, you can get one from me directly (for $15) and save the shipping cost.
How can I contact you? Contact me on twitter or via e-mail at info AT iamiran.org