If you are somewhat handy with a soldering iron you could make one without much difficulty. I made my own db-25 to rca six-channel cable. I found a diagram of which pins correspond to which channels, and used a db-25 connector from radio shack and some spare cables. Works great.
I would definitely try to make my own cable if I had some sort of diagram of which pins correspond to which channel.
I did a search online but could not find anything. If you have that diagram still kicking around do you think you could e-mail it to me.