Costumes for The Artist were designed by Mark Bridges, who won an academy award for best costumes. This gown appears to have been purchased from the company Leluxe Clothing, which specializes in beaded flapper era gowns, and has a bit of a history of having their gowns show up in various hollywood productions. While these two gowns may not be the exact same piece, the idea that they could be is not an impossible one. Even clothing that is purchased off the rack by designers usually winds up going into the rental stock of a costume house, and it could easily have been pulled for use in Once Upon a Time. The fact that this gown has not been available for quite sme time from Leluxe (though it is still available in copper), and would not have been available for purchase during the filming of this episode of Once Upon a Time lends credence to idea that these could indeed be the exact same piece.