SOURCE: somewhere on the Internet

If you have an electric start model with a 12v battery in it, then it already has a rectifier/regulator and you can wire right off the battery. If not, you'll need to put in a rectifier (4 diodes) with a large capacitor and a voltage regulator (7812) circuit to power the GPS. Then you can put a set of lithium batteries in the GPS as a cold weather backup to the hard wired power supply... in the event that your sled dies and you have to walk home.

PartPart NumberPart Description (from Radio Shack)Price
IC1276-1161ASilicon Bridge Rectifier 200V 1A$0.99
IC2276-1771A7812 12VDC Voltage Regulator$1.49
C1,C2272-1044100 uF 50W Capacitor$1.19
C3272-1350.1 uF 50W Capacitor$0.69
C4,C5272-10700.22 uF 50W Capacitor$0.89 (pkg of 2)
D1276-56415V Zener Diode$0.99
270-283AProject Enclosure w/ PC Board$1.49
270-026DC Accessory Cable$1.49
270-1211Fuse Holder$1.49
270-10031/2 Amp Fuse$1.29 (pkg of 4)
Total Cost:$12