You could try Vuplex. Can buy it at autobarn for like 12-20 i think i forgot. Worked on my mates evo, not going to say was it went back to perfect condition but I saw a big difference.

If that doesnt work then its most likely from the inside, try opening your headlights by letting them bake in the oven should be a DIY somewhere here then use your products to try clean it.

If that doesnt work then I'm pretty sure you can buy the lense from Peter Warren Sydney Auto World. Could give them a call and ask them.

Hope this helps. Goodluck!