I've seen a few requests for this before, like in this thread: http://www.t-shirtforums.com/wholesale-t-shirts/t10726.html

SanMar.com has some apparel made of Modal.

Modal appears to be similar to rayon in the way it's manufactured and by the way it feels. I think Modal and Tencel are different trademarked names of a type of fabric made in a similar manner (similar to the way Bamboo tees are processed)

You may want to try a bamboo/organic cotton blend t-shirt to see if it fits the style/fit/feel that you're looking for if you can't find Modal.

 

Thanks a million, I will research this!