I have just last week installed some headlight and fog light covers from Lamin-x Protective Films on my 01 WRX. I lost one of my old clear perspex covers on my RH Fog lamp and looked for weeks for a replacement in shops and on the Net
These are thin film laminated stick-on covers that are available in clear to dark tint.
May not protect glass against rocks but are quoted to protect against the day- to-day sand blasting and stone chips.
Dont know if anyone else has had any experience with these covers but they were relatively easy to install and look good.
I will put up some pics in a day or so.