Okay here's what you guys need to do. Google search "(province/state you live in) stainless steel mesh". For example, I would search "ontario stainless steel mesh", and a bunch of websites for Toronto mesh sellers pop up. I see Ferrier Wire sells stainless steel mesh, so I click the website. Then I select their stainless steel mesh, and look for the appropriate thickness and spacing. If you guys need help picking appropriate mesh, just tell me where you live. Like, I don't need your street address or anything, just a major city you're close-ish to. I have an aviary in the basement, so I know all about appropriate mesh, hardware, etc.
If a product says "steel", rather than "stainless steel", assume it's galvanized, since stainless steel is completely different from "regular" steel, and the seller/manufacturer would definitely label it as stainless steel if it were such.
Okay, rescuebird, here:
https://www.twpinc.com/wire-mesh-material/welded-stainless-mesh
You'll want the T316 since it's stronger against corrosion than the T304. If it was for an indoor aviary, I'd get the T304 since it's supposed to be better for getting food and poop off of. You'll probably want the 1" .080", but the 1/2" .063" might work, since it's a closer weld and would be quite sturdy. I know the link I sent you is for welded mesh, but this specific weld uses pressure, rather than filler metal. I don't have experience with how strong Amazon beaks are, but the mesh is probably strong enough.
Then I'd attach the edges together with long, stainless steel angle irons and stainless steel bolts and stuff. Stainless steel angle irons on both the interior and exterior of the aviary, sandwiching the stainless steel mesh together. It'll be a nightmare figuring out the door, though.
Oh, since it's outdoors, you'll probably want to dig a trench around the aviary to fill with cement so rats or whatever can't burrow in.