I found a great source of shoes for the female figures. The prices are pretty cool, but they soak you on shipping.
They are from parabox in japan, and the ones you want are the 21cm shoes.
I just got two pairs of Mary Jane like shoes for 5 bucks a pair.
However, the shipping was 18 bucks, which shocked the snot out of me.
You might want to drop them a line first, before ordering and see if the price is constant for large orders.
That way, you can buy shoes in bulk.
They also have boots, clothes, bikes, wigs, heads, and bodies.