Cleaap orr stick on Stone protector on front of van

3M make a clear sheet a few mm thick which is sold for headlight protection, you can buy it at auto accessory places precut to suit vehicle headlights or in rectangular sheets that you cut yourself, they would be a bit small to do the front of a van though as the biggest sheets I've seen are about 500 x 200mm.
It works well on headlights, stays clear as glass, doesn't yellow and will hold the headlight intact after a severe impact. I had a couple of richard craniums lob a half brick at the front of my old 740 Volvo years ago as I was driving home from work and it hit the headlight on the bounce at about 50kph, smashed the glass but it stayed intact for several years afterwards held by the clear sheet stuck on the outside.
I have seen large sheets available in RV places in the US so maybe it is available in Oz too.