An American friend sent my (Wizard of Oz obsessed) daughter a pair of Walmart 'ruby slippers' when she was little.
These 'ruby slipper' shoe covers from Amazon are a good idea too, ie, you can wear them over regular shoes and don't have to worry about growing out of them:http://www.amazon.com/gp/product/B000OW8ZV...P84YB6JWZSD6FGG
I don't think they ship to Australia but you might be able to find someone else that makes them here (or suggest that they do).
This person on madeit makes cute little kids shoes to order. She might be able to make something appropriate to go with a costume:http://www.madeit.com.au/detail.asp?id=564916
Edited by mrsjessop, 21 June 2012 - 11:39 AM.