Any coaxial phono-phono will work in a short length. So you probably have something lying around to get you going.
If the DAC you end up with has TOSLink or uses BNC for S/PDIF then your options spread. Given that most S/PDIF is phono clearly impedance isn't critical so don't worry about it too much. Maplin sell adaptors and ready made cables, or any music gear type shop will be able to help.
Paul