I found a partial solution to foggy headlamps since replacement headlamps are at least $100 each for imported salt water salvage parts.
Get a spray bottle of bug spray with DEET in it. Can be found at Bass Pro, Cabelas, Gander Mountain or any outdoor store. Spray it on the lens and wipe it off with a paper towel. It does not make them look like brand new but it does a great job for ten dollars.
Keep in mind that they will yellow again since the UV coating is already worn off.