this stuff rocks, and you can get it in colors other than black and it comes in several gage sizes.
places like Fry's Electronics or Microcenter also carry these kinds of products for electronics techs/enthusiasts that do repars/mods.
it can also be ordered from online sources like Mouser and Digikey but there's nothing like being able to see it and decide what works best for your detailing.
alternatively, you can disassemble old electric motors/alternators/generators (even electric fans) to get various sizes of wire for free is you have dead electrics laying around.
dead floppy or dvd drives have a ton of parts that can be used if you don't mind taking them apart.