You have to use an Apple 30-pin to lightning adapter since it includes a digital to analog convertor. The lightning connector only has digital output so you won't find a single cable to accomplish this.
Using a 30-pin to USB and Aux Y cable with the Apple 30-pin to lightning adapter should work for you. Apple sells a 0.2m adapter cable that probably works with your case. I plan on doing this setup myself since I haven't found any other way, and no company makes a single cable that has USB, Aux, DAC, and lightning.