Just about any orange wire in the harness will get you a supply of power - but it may not be clean. You could also use the running light wires that to the bulb in each of the front turn signals.
If you use one of the existing wires in the harness, the digital volt meter may jump around whenever you use the turn signals, horn, brake lights, etc. The harness has a lot of interconnections and the power may not be steady. The first time I hooked up my tach to a power wire in the harness, the rpm reading would spike with my turn signals and my red rpm limit light would come on.
You could try tapping into the running lights in the headlight bucket, and if the reading is not steady enough you will need to find another source or do what Verslagen suggests....and run a + and - wire to the battery....that will be the steadiest and will most accurately reflect what the battery is doing.
Here is a link to the wiring diagrams, that will help you decipher the stock wiring.
http://suzukisavage.com/cgi-bin/YaBB.pl?num=1294779818Dave