This is an old thread but we have some info that might be handy for DIY types. The suggested toslink adapter is just about gone unless you can find an ebayed XMPCR that was converted. The good news is that the DIT4096 IC is available but it is a hard to home solder (for us) tiny surface mount package. Ebay does have some presoldered DIT4096 to 28pin DIP carriers. The toslink socket (TOTX173) is obsolete but can also be found on ebay. The project schematic seems simple enough; DIT4096, TOTX173, a 10K and a 8.3K resistors and maybe some decoupling capacitors (recommended by TI but not used in the obsolete toslink adapter nor on the located schematic).
the schematic can be found at http://www.devrs.com/store/MyRadioStoreKit.gif. Note there appears to be a minor error on the schematic. Pin 7 is Vio according to TI. It doesn't effect the build as the wiring to that pin seems correct.
The resulting build will be much larger than the suggested toslink adapter but has the advantage of being available and more easily connectable to the Directed HD Radio.
link to presoldered DIT4096 to 28pin DIP carriers (DIT4096I ON SOIC28 to DIP28 PCB)