I don't know if PartsShop can get these or not. If not, and you can't get them at a auto recycler, there are 2 ways to go, assuming you are looking for yellow light from your fog lamps.
The first way is that Hella, Osram-Sylvania, and maybe Philips all make a yellow series H1 bulb that has an optical coating. I have the yellow H3 bulbs in my fog lamps, as the yellow reflector went away with my US light assemblies when I switched to Euros. The yellow light is a "softer" yellow than the old ones.
The second way is that a lot of the "rice" specialty shops, and http://store.autotoys.com/cgi-bin/wfp53024.storefront/
carry colored caps to fit over various bulbs.
2003 Firemist Red/grey leather SL 500
2015 Palladium Silver/black mbtex GLK 350
1987 Smoke Silver/burgundy mbtex 300E Sportline (SOLD)
Click to see 87 300E