Well
they come in three, five, ten, and fifteen-foot kits from $19.99 to $69.99 (according to StreetGlow). Says there that they run on 'low voltage,' but that means something totally different for a full-scale car. They look like they'd make great underbodies, since you can cut them to any length once you get them.
Might just do that.
Ok, I just found out that they use 2 AAs, which equates to three volts. I don't know if I can fit another two AAs under the body, it'd be screamingly tight at the very best.