If there were such a gadget, it would probably be more expensive than the new cable release.
The MC-DC2 (usb) cable release is only about $25, so you shouldn't worry about getting a new one. It's not nearly as expensive as the 10-pin cable release from previous cameras. And it's easier to use, too.
One more thing, the IR release works from the back of the D-600 too, so you don't have to reach around your tripod to trigger the camera anymore.