OT - Buying T-shirts in Bulk, any tips?

[ferrytale]

I figured I would ask here to see if anyone here has any experience with a good company to purchase bulk tie-dyed t-shirts. I am an experienced Tie-dyer, however, my co-leader and I were hoping to surprise our Girl Scout troop with tie-dyed shirts screen printed with our fun "logo" that the girls came up with as a surprise, and I just don't have time to tie-dye 20 shirts and I don't know if the screen printer will take them if we have dyed them ourselves.
Please let me know if anyone knows of a reliable place that is reasonably priced and good quality. Thanks!