Don't forget to check your local library too!! I just got a couple of books from there with sweater patterns for that size!! Here are some you could look at:
Big Fish, Little Fish - by Jil Eaton
Minnowknits too - More Uncommon Knits - by Jil Eaton
Easy Knits for Kids - by Vogue Knitting
Nifty Knits for Kids - by Catherine Ham
Bright Knits for Kids - by Debbie Bliss
All these are at my local library! Happy searching!!