Do you mean family t-shirts where everyone in travelling party wears the t-shirt them maybe visit your local t-shirt printing shop.
I'm not sure if shopDisney do family t-shirts but you can always visit your local shopDisney store and ask them.
I agree about Tee Public. I got a whole assortment last year for my WDW trip. Tshirts are a great quality, wash well, wear well and the selection is amazing. Just give yourself plenty of lead time.