This one is pretty simple – a scaled-down replica of the Kryptonite chain that Superman wore (against his will) in the first movie. It was cleverly bestowed upon the Man of Steel by Lex Luthor.
It really pains me to say this, but the makers of Smallville did something right in allowing fans to buy a replica of the Kryptonite chain worn by Lana in the first few seasons of the show. Very forward thinking. But alas, nothing from the first film is currently available.