TH, I don't know if that particular cable is available commercially, but you could certainly replicate it from items which are available, e.g. two RCA to one 1/8" Y-cable plus 1/8" to 1/4" adapter plus 1/4" to 1/4" coupler for your headphones. Or, as Brandon(haoleb) suggested, he or someone could make it as one piece.

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Enjoy the music, not the equipment.