I ran into the same problem when I bought my Sony DAV-FX10 home theater system. It has 1 optical input and 1 coaxial input, but I needed 2 optical inputs. So I searched the web for a converter and found this:
http://www.amazon.com/DAYTON-DAC-OC-OPTICAL-COAXIAL-CONVERTER/dp/B0002MQGQS...