These were my favorite shorts last summer for Olive. So much so that I bought 4 pairs and bought the same ones for this summer! I have 2 in blue and 2 in white. One of the white pairs is 18-24 months and the other 3 are 12-18 months.
They ran a little big on Olive, but she was a skinny mini then. The reviews say that they run true to size. In the pictures below she is 21 months.
Old Navy is selling them right now:
http://oldnavy.gap.com/browse/product.do?cid=66823&vid=1&pid=939853022
http://oldnavy.gap.com/browse/product.do?cid=66823&vid=1&pid=939855002
Asking $12 shipped.