It may not be what you are looking for, but if you haven't already checked them out, try www.cafepress.com.
They will print your designs "on demand" if you set up a shop with them. They have a free level and one that is $7 per month. You just make the designs, set up a shop and when you make a sale they print, ship and collect the $ and you earn a commission.
This is just one the first digital textile printers I came across.
Digital textile presses are fairly new technology but they have been around long enough to think about getting one offs done that way. Remember you don't have to pay for screens but the more work they have to do on your art the more it costs. So find out what files they deal with and how the files need to be saved. If you can furnish a file close to what the use that will save you a chunk.