W123 Foglights.
 

My foglights don't work. Till I get enough things out of the way to invest in some euros, could someone tell me if I just bought the right sized sealed halogen, and put them in just for looks, would a normal bulb mount into the opening? If so, what size?

Your W123 fog lights already have removable bulbs (H4 I believe). If you are getting power to the lights, just replace the bulbs. I don't know of sealed beam lights in that size.

See, my problem is that before I bought the car, someone punched out all the front lenses. The main headlamps where easy, cheap. The foglights, however, require a new assembly, and I just don't want to spend that kind of money on something that I will rarely/never use. Also, I don't like the yellow color too much. I'd rather have something clear.

Early-year W123s had clear foglights. Later ones got the amber lenses. Dealer will have both, as will salvage yard. There's really nothing else to put there and that will save rewiring, too.

Aren't the foglights the same size as American cars had -- the quad headlights?

I would look in your local bone yard. I know of a pair in the one I go to all the time. If you want me to pull them for you let me know...