The Browser has an interview with Yana van der Meulen Rodgers, director of the Rutgers University Project on Economics and Children, in which she recommends a bunch of picture books with economics lessons. None of them are exactly what you'd call Austrian, or even Milton Friedman-style, as far as I can tell, but maybe there's an opportunity there. One of the books is by, of all people, Sheila Bair. At least the list doesn't include The Rainbow Fish.
Economics Books for Young Children