Hi Chunner,
My 91 318is does not have fogs either. I bought some fog light housings off of ebay and threw a new set of lenses on them. So far as I can tell, my car is not pre-wired, so my plan is to wire it myself. I bought a fog light switch and hacked the plugs for it and the housings out of a donor car. All that is left is to wire it to the switch and the fuse block.
I'll take some photos and write up a DIY as soon as I get it done.
-Sal