You could get oil/water-base acrylic silkscreen paint to write the text on a cotton shirt.
If you do not care too much with permancy, then get some water-base Stevenson acrylic paint at you local art store to do the job, or a good quality acrylic house paint subtitude (just thin the paint with pain thiner/water to let it soak into the fiber)
If you use a white shirt, then cotton dye or india-ink would do it too.