what, you don't want to pay yaesu $60+ for what amounts to a 20 foot phone cord and a piece of stamped metal??
look at the short cable between the control head and the radio...I think it is a typical flat 6 conductor cable with 6 pin modular plugs, but the wires are flipped 180 degrees between them...should be easy enough to make one, you'd just need crimpers that can do 6 pin modular plugs. cat5 is fine, you'll just have two unused conductors.
just make the ends the same as the stock cable and it should work fine. I've been meaning to do the same thing with my 8800.