What is the input to your card optical? Is it toslink or a mini optical input like the iRiver? You can get a mini to toslink or mini to mini optical in most lengths you would need. I would not go over 3 feet or so but you can longer. You can get excellent quality optical cable in any length and end termination
Sys Concept Inc. Fiber Optic Products Attenuators, Patch cords, Laser Diodes, Connectors, MP3, Toslink, Hybrid Adapter and more: Toslink to Toslink Premium Optical Cable 0.05 to 50 meters
Email Joseph with the length you need end to end and what termination you need. He provides excellent service. I have used his optical cables for a number of years now as have others I have given this information to.