I need more bug screening material for my 1939 Pueblo Revival house, both to make additional window screens and to stuff squares of screen into the basement and attic crawl space vent holes.

The original screening is metal and fairly rigid. I went to Home Depot and got aluminum screen but it's way too flimsy. I used it anyway for the crawl space holes but discovered that the ground squirrels can just push it aside. (This is not true of the original stuff. It takes pliers and a lot of pulling to get this stuff out of the hole. It is tough.) So now I have a ground squirrel problem. :(

Anyway, after I do some trapping, I need to get some decent, tough screening to permanently close off those holes. Any sources for this?

I've gone hunting at the local salvage yard and have found rusty old window screens with the material I need but they are (oddly) on the pricy side and I have 60+ holes to fill. Any thoughts?