According to the Twilight Examiner, Kristen's actual dress will be up for display along with other dresses designed by Elie Saab.
Kristen Stewart's premiere dress for The Twilight Saga: Eclipse has been chosen as one of "twelve Elie Saab gowns, famously worn by international celebrities on the red carpet over the years . . . [included in an] Elie Saab showcase . . . at Harrrods [which will run] until 22nd December, in the store‘s Luxury Collections Display Lobby, First Floor," per Bloginity.
Other stars whose dresses are included in the showcase are: Gwenyth Paltrow, Helen Mirren, Beyonce, Diane Kruger, Halle Berry, and more.
Stewart's dress was part of Elie Saab's Haute Couture Autumn/Winter 09-10 collection and is pictured on the runway (left) via ElieSaab.com.