Spdif source switching?

This may not be exactly what you had in mind, but it might work depending on your situation. The Monarchy Audio DIP Combo allows the user to switch between a line input and an optical input. You might experience sonic improvements as well depending on your DAC and your sources.

If you have basic DIY soldering skills you can combine

http://www.twistedpearaudio.com/control/otto.aspx

with a Twisted Pear Placid power supply in an ebay-sourced enclosure.

The optimum device would be a Sychro-Mesh. It is the best reclocker on the market and has Toslink and coax inputs with a selector switch. The SM will improve your audio quality significantly by reducing jitter. I used to mod the Monarchy DIP. Even with mods, not even close. The SM has money-back guarantee, less shipping. If it does not knock your socks off, return it.

the Synchro-Mesh:

http://www.empiricalaudio.com/products/synchro-mesh

Reviews:

http://www.empiricalaudio.com/news-and-reviews/synchro-mesh

This will be the best system upgrade you have ever done, and its the right place to put your money. More important than even the DAC.

Steve N.
Empirical Audio

how about this ?
http://www.cs1.net/products/audio_authority/1177A.htm#purchase