Good source of power for aftermarket fog lights

Hello. I am glad I found this forum. My son purchased an aftermarket fog light kit for his 2012 Mitsubishi Galant ES. It has all the wiring and connectors and relay and fuse in the box. It is a Spyder kit from what I can recall. Anyway I was wondering what would be the best place to run the positive from? He has the switch which fits right in the dash and that would turn it on and off. He said he would like it to hook it up when he would turn off his key that the lights will go out automatically without having to think about the switch. I told them if we can find an accessory wire that would possibly work. I am not sure if there is one in one of the fuse boxes in the car that could be used since I have not looked at it yet. If anyone out there would have any good suggestions it would be greatly appreciated.