There are so many wonderful vendors right here on YT!!! You can see the list of them in the vendors threads. We love go-fetch nighties for those cold evenings.... and I know that LuvMySissy makes some beautiful dresses (we got one at the meetup in KC and it is so adorable). We also have some sundresses from CRB..... and also some shirts (personalized) from POCOMUTT. There are so many more that I haven't mentioned that are also wonderful. I would check them out first!
You could also look at Petedge..... the stuff is reasonable BUT you have to consider their shipping charges and it gets very expensive.