How about BarkinDog clothes.....I think their link is
www.BarkinDog.com, but I am not sure. I know that Joy posted in My Yorkie - Jaden bringing sexy back...that shirt was made there. They will put what you want on the shirts.
And around Christmas time, PetsMart (online) had a thing where you picked out what shirt or tank you wanted and could have whatever you wanted put on it. You might can check that out too.