Just find a longer IDE cable, cut one end off and separate the wires as you have done on that one. Then crimp some quick disconnects onto the ends of each wire and away you go.
I had to do that recently on a friends minipac as the wiring harness that comes with the minipac is way too short for a large panel. Most local computer shops should have old IDE cables laying around out the back which they may let you have. I managed to find one which was about 40cm long and only had the connectors at each end and it worked out great.