I've been very happy with custom products from
www.CafePress.com. You can put any image you want, even full color (e.g.
a FIRST Logo). They were fast, but I was only ordering one item in each order. I've never ordered from them in bulk. 18-23 t-shirts are $12.75 each for dark colors and $9.75 for light colors. It goes down in price if you order more.