Perhaps the Museum of Modern Art?
http://www.flickr.com/photos/wallyg/562286070/
Found by a web search using the terms
Andy Warhol  double Elvis Presley silkscreen
 
There are other hits as well.
Barbara Hass, retired librarian
 
 
In a message dated 6/5/2009 5:40:16 P.M. Mountain Daylight Time, [log in to unmask] writes:

Please excuse cross posting.

For an exhibition next January, the National Portrait Gallery is hoping to borrow a Ferus type silkscreen by Andy Warhol of Elvis Presley.  It must be smaller than 82 inches wide to fit the particular gallery for the exhibition so a double or small triple portrait would be ideal. 

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