The one I linked was the first I found on amazon with a S/PDIF connector. I'm sure there are many others out there. A USB DAC would get the job done too.

I've had an A7N8X ASUS motherboard (etc) for awhile now. I'm just now wanting to get an optical SPDIF connection to my stereo. My only digital coax connection is taken by my cable box, but I have ...

This can provide a direct S/PDIF output from your PC. Avoid Analog Conversions: Avoid using analog to digital conversions (e.g., 3.5mm to RCA to Optical) as they can degrade audio quality.