Just to be sure everyone knows their regulators from the rectifiers, here is the scoop.
Regulators; Almost all modern sleds produce AC voltage from the lighting coils for elcetrical use in the sled. Light bulbs ( not LEDs), handwarmers, gauges, coils all work just fine with AC voltage, but need a voltage regulator to keep from blowing stuff up. Again most sleds have a very simple voltage regulator that just basically chops off high voltage a some point, usually 14-15 volts, and sends it to ground. It does not regulate low voltage, hence the light dimming as mentioned above.
Rectifier; A rectifier is needed to convert AC voltage to DC voltage. Why do that, well if you have an electric start, DC voltage is needed to charge the battery. A rectifier does not regulate voltage, just AC to DC, but to confuse things there are combination regulator/rectifier modules out there, as most street bikes have them. Soo, all electric start sleds have DC voltage, and you would be OK to hook up a cigarette lighter socket to an electric start sled and would be good to go. No electric start on the ZRT, then as said above you will need some kind of recitfier module to convert the AC to DC, because 12v DC is what your GPS adapter needs.
Hope that is as clear as mud. Yeah, I know a lot of new sleds have electronic ignition comtrols, without electric start. How? These modules have their own voltage power supply components on board, and are hard to tap in to, and usually do not have enough excess capacity to run external devices.