Start off by going to checker or some place and get a "headlight resoration kit." You essentially wet sand off the scratches (with sandpaper increasing in grit count all the way up to like 5000 grit), you then polish it with a plastic polish. I've done it on several cars that have beat up, oxidized lenses; works like a charm. Then get some of these: Lamin-X
. I won't lie, I got a set of those for my 06 CBR and they were a little bit bigger, but you can trim them (I addressed the issue with them and they were unaware there was a size problem, they may have fixed that). They really are a good product tho, good quality construction and good customer support
Oh yeah, the resoration kit costs like $15 (it's worth a shot, and it's easy) and if you get the films it's another $24.95 if you want to keep them "like new"
Total = $40, 30 min, and very little effort
(If you want, I have before/after pics of the car headlights I've done. I can put them up when I get home from work)