Kate Middleton wore Reiss' "Nanette" dress (from last season) for the official engagement photos. Although the dress goes for about $284 and will be available this month as part of the Reiss spring/summer 2011 collection, you might want an even cheaper version of the look.
Consider the Patrizia Pepe Shoulder Pad Fitted Dress ($101.72 at ASOS). Top the number off with a white cropped sweater, and you've got the look!
Photo Credit: Getty Images (Courtesy: iVillage)