Hi Sean,
Cavalry to the rescue once again
If you are after Barracuda type netting then the article that Phil refers to is on the
Plastic Warafre site.
For the older type netting with strips of hessian, then there is an article on
Missing Link . Just a point to note, this type of netting stopped being used on AFVs in NZ after about 1977, we had a little accident
Or if you are after scrim, like these M577s

I would suggest some fine fabric, maybe an old (well worn) handkerchief or the like.
cheers
David