My feet are too small to wear womens shoes?

i need to find a decent pair of heels for senior formal and my feet are just too small to fit size 5 womens (australian sizes). i ma not going to wear childrens sizes becasue they do not sell good heels for childerns sizes is there any way that i can buy a decent pair of heels for a good price that will fit me? (my feet are 22 cm long; 8.5in.) do i have to buy shoes online or overseas because i am on a budgetm. or is there a shop in sydney australia that sells shoes that are smaller than size 5 womens?