From what I'm reading here you want 8 mesh hardware cloth. I was able to find small rolls at True Value. I purchased a roll of 6 mesh from Argus Steel. This is galvanized steel .035 size wire, pretty stiff material. I use it for my SHB bottom board traps. The consistency of the weave leaves something to be desired. I have also found that the size of the adult beetles vary. I think gender is the reason. I have found aluminum 6 mesh here
My next purchase will be the aluminum. It looks very similar to the screen available from Green Bee.