Thanks to a Roku forum user for this one:

Part number CRE-ZVM-AV-STR sold from ITDirec ships for less than $4.00.

It’s a Creative Zen video cable, but the pin out is the same as the pricey component cable sold from Roku.

The original post is here.

You will need to plug the cables in according to this chart:

The RED RCA jack goes to Y or GREEN RCA input
The WHITE RCA jack goes to Pb or BLUE RCA input
The YELLOW RCA jack goes to Pr or RED RCA input

The above chart and cable are just for component video. You will also need to use either the RCA stereo audio cables that came with your XDS or connect to your TV or receiver with your own digital audio cable.

Pinout information here is:
1 = Ground, 2 = Red, 3 = Blue, 4 = Green. Also verified that it is the same as the component cable supplied with the WD TV Live and Live+ units. For reference, pin 1 being closest to the jacket and pin 4 being the tip of the jack.

See picture and more information on the pin out here: