Lead for my cd changer to work std head unit

Hi Guys,yep im new to the landy zone forum,now on my second disco and loving it.One simple question for you brain boxes out there,my disco has the head unit controls on the speedo surround ie volume up and down,next and sel to select a cd or wave band(my disco is a 1998 300tdi gs model)i have been told i can fit a non land rover changer unit to the standard head unit via a lead,i have a kenwood kdc467 cd changer unit already,where do i purchase a lead!!!please help the radio is boring the hell out of me,thanx Paul.