I hooked my Zumo 550 up this weekend using this method. First call your dealer and order this plug below. It will cost you about $25 dollars. It is called a repair connector. This connector will keep you from having to cut the plug off of the wiring harness by your steering column. It will plug directly into the power supply. It is important to only use wire #1=Brown(Ground) & wire #3=Hot. Just plug wire #2 off.
Part #PN is 83300413585
This is what it looks like connected to the factory power supply. This plug is not powered all the time. There is a 30/40 second delay before it shuts down after you switch the ignition off.