Moved to First Generation Focus Non-Performance Discussions. Ford Focus Technical Chat is for maintenance, engine problems, and recalls. Thanks for posting!
As far as I understand, if you can find factory fog lights in a salvage yard, you should be able to simply pop those in the bumper, plug in the wiring, and replace the light switch in order to add Fog lights. Don't forget that light switch if you want an OEM added fog light to work.