J.C.
Are you by any chance an Intercultural parent? I'm laughing remembering the same search many years ago - my son started in January when the stores were cleaned out of slippers. (a friend rescued me with her old slippers). I may have some in that size - I'll PM you if I can turn them up this weekend.
You could try Leo's (the dance place in Galewood) for ballet-style slippers. And I did see kids' slippers about 2 weeks ago at the Sears at Oakbrook, in the Lands End section against the wall. (I'd call first, though.)