Based on the electrical diagram of the Monster 1200, there is a Sumitono HM-90 connector under the tank ( front ) on the left side.
This electrical connector is fused at 7.5 amps or 90 watts and is activated when you turn on the key.
P.S. As always...used at your own risk!!!!
This circuit is fine for GPS, Radar, Heated Grips. However, if you try to run heated clothing as well, you will very likely exceed the circuit capacity. I tried it and blew the fuse. My heated grips are about 2.5A. My heated jacket liner and pants liner are about 7-8A at highest setting. I subsequently wired my heated clothing directly to the battery. The heated clothing (Warm & Safe) harness comes with a 30A fuse.