By lala002
I don't know about the accessories, but I think the dress part would be pretty easy to make. There are probably patterns in the popular catalogs (McCall's, Simplicity, etc). Or, there are some simple directions for different styles of Greek clothing here:
www.dl.ket.org/
You could try your local thrift store, they have all kinds of kids costumes there, or you might be able just to find a white dress and the accessories to make your own Greek dress for just a few dollars.