This skirt actually started out as a slip! Patricia Field loved the color and design so much, she used it as the skirt. This outfit is compared to her short tutu from the series intro scene (learned from here).
Want to get the look? You can actually get this same t-shirt on Ebay.
campojari seller - Buy it now for $50
Skirt options:
Short style in that pretty purple by Asos
A fuller skirt by Alloy
For a more tailored skirt - J.Crews brilliant purple skirt
Updated: Just found this exact knock-off of Carrie's skirt on eDressMe if you are looking for something more exact:
Updated: Just found this exact knock-off of Carrie's skirt on eDressMe if you are looking for something more exact:
And another update - shop all the SATC 2 clothing styles and get 30% off now through tomorrow (6/2) using code: satc2
You could also dig out an old prom dress and repurpose the bottom half for a skirt... :)