Hi TigerRag,
I think you will find it hard to find someone who would print just one at a time, it's not worth it, it depends how you want them printed and how many colours and what colour t-shirts.
I would say you need to find a
DTG printer, but you might just have to take the plunge and order 5-10 shirts but even then it will be costly.
Open a spreadshirt shop and see if the designs sell.
Lee