In case you missed today's airing of The View. It's already online.
At first, I thought Michelle's dress was by White House/Black Market (which made me laugh in that tongue in cheek way) but is also sold on the site of WHBM designer Donna Ricco. It retails for $139 and $99 depending on which site you buy it from and there are still a few left so godspeed MichelleOphiles!
ETA: The dress is now sold out. Better head to EBAY. Article about the surge in demand for the frock.