I have conducted 3 bike tours down the Calif coast for my Varstiy Team (400+ miles). This last time we had custom cycling jerseys printed. They were designed by a scout for his high school graphics art class. We used Champion System. There are some initial fees, but once that's done, there is no minimum on size or quantity (if memory serves me). They provide fully custom sublimation printing (needed for jerseys, lithographic printing doesn't cut it). Contact me if you would like to see what we did.
We also had custom activity uniforms (t shirts) printed so they were still "in uniform" once in camp, showered, changed, etc.