Looking around the sites I linked a bit more, this one looks like a likely candidate:
http://www.bluespot.co.uk/stock/auxin.asp

Looking at the pic, it very much looks like it's plug compatible with C3 (3+2+3 pins in 3 rows). The 3.5mm plug looks like it connects to pins 18 (for ground), 19 and 20 (for L & R signals). You'd need to either snip the plug and attach RCAs instead, or get an additional 3.5mm female plug <-> RCAs adapter.

/Michael