If anyone finds a place to get the covers:

Headlights are easily busted apart by warming in an oven at @250 degrees for 5-10 minutes.
Do a Google search for "clearing headlights" +"WRX" -we Subaru guys used to do this all of the time. I've done a few sets myself.
This method maintains the 'goo' that seals the lights, and no other sealant is necessary upon reassembly.

There are also numerous online tutorials for polishing the plastic lenses using basic buffing tools (wheels and compounds). If a 40 year-old muscle car's turn signal lenses can be brought back to life, than I figure that ours can't be too far beyond hope.