If you want more light out of the stock fog location, I would recommend finding some Hella, PIAA, or Pilot lamps that are the same size as the stockers and putting them in that slot. IMHO, the stock fogs suck: I haven't used mine for 2 years and got some Pilots. To answer your question, the stock fogs use 899 bulbs I think. PIAA might have some superwhite replacements, but you might as well get new lamps. Also, don't try to use factory wiring with new lamps, the new lights should come with new wiring and stuff. I would recommend any of the above brands. Pilots are good quality budget lights that come in a complete kit. Hella's are a bit more expensive and hard to install (from what I hear). PIAA's are expensive, but easy to install and high quality.
I haven't had any problems with my Pilots, but many here swear by PIAA.