Might be a better way, but the only thing I can come up with is to mail it to yourself. When it arrives, tap and hold on the picture for the popup menu, then save it. It will not be in the Camera Roll and Photo Stream. You can delete it from the Camera Roll and it will stay in the Stream.
On the other hand, a better way to move older and iTunes synced pictures directly between devices is PhotoSync. It's a universal app, so buy it once and download it to both devices.