Mike, you may want to consider putting them on Cafe Press. We set up a free shop for the NLDA and recently uploaded t-shirts to commemorate our Hunt for the Hungry sponsorship. We were able to make several options available so people could get whatever size, color or style they wanted. Obviously you don't make as much money, especially with double sided printing, but it worked for our budget.
http://www.cafepress.com/lacydogDJ and Amber Middleton's son modeling the baby shirt option, this alone was worth going with Cafe Press!
