Etsy may be a good place to search. A friend of mine just posted her daughter's 2nd birthday outfit on facebook, it was a shirt and tutu, ADORABLE! You may just want to search and see what comes up.
I had a custom made one for dd#2 that I bought on ebay. Try searching birthday dress or boutique birthday dress there. DD#1 had a smocked birthday dress but it wasn't personalized. It came from a children's boutique.