This looks like 4 x 4 to me and it's often found at the hardware store in the fencing aisle. Too big for code? That is odd. Code sorta revolves around the fact that a child should not be able to slip his head in the openings. 4 x 4 should be fine. I'd ask more questions of your code advisor.

Ha! Yep, that's smaller than a newborn's head, and they don't generally go around sticking their heads in things. Still, code says a 4" diam ball cannot pass through any opening, so I'll test some 4x4 sheets I found at a local ranch store. Seems if the mesh is 4" on center, and the gauge is hefty enough, I'll be ok.

Just saw your question. You have probably moved on to new projects. Yes, this is 4x4 welded wire mesh.