I buy EL wire from ELWirePros.com - reliable, reasonably cheap, and reasonably reliable. I havn't put it on a game yet (I don't think it would look good on TZ, and I don't think i'm going to keep No Fear, though it'd look bitchin with some super-bright orange on ramp) - I use it to make glowing posters/murals/whateveryoucallem with geometric patterns on them.
I don't know if they have any inverters that will run off the ~6v of GI lighting (i know they've got 3v ones, and 12v ones, and 9v ones, but not sure about 6 - a 6v one designed to run off 4 batteries would work on 6.3 though). I know the Stern machines have a 12v header available for aftermarket use (thanks Gary!), but for older machines, you might end up taking directly off power driver board.
Generally speaking, soldering the leads onto EL wire is unpleasant, avoid it if you don't need to make lots of odd lengths; The wire has a solid copper core covered with hard-to-scrape-off phosphor on it, which needs to be scraped off. That's one wire. The other wire needs to go to the two hair-thin wires wrapped around the phosphor-covered core. Can't see them? That's because you cut through them when you stripped the plastic off (or because you don't have your reading glasses on). Those hair-thin wires are very hard to work with.
Not sure what to say on how to attach the EL wire. All I can say is that epoxy doesn't work, and neither does hotglue, unless you totally surround the EL wire in hotglue (it doesn't stick).