Good battery powered Toslink optical DAC needed

Anyone know of one? I have checked the Ack-Industries and Scott Nixon Battery operated D/A converters but I have been unable to find one that has a Toslink input for digital signal. Is there any made? Thanks for the interest.
I am under the impression that toslink is just about the worst way to connect anything in terms of signal quality, anyone know if I am correct?
California Audio Labs Gamma will work on 12 volts. I used to have it installed in my car stereo.
Scott Nixon offers a toslink input as an approximately $30 option to his NOS dacs. There is no switch between coaxial and optical, so you have to be careful to have just one input active.

I'm curious. I have a Gamma unit hanging around right now, unused. What did it take to get it into your car system -- hard, easy? How vast an improvement has it made?

Thanks -- Tom