Source for Expanded metal/mesh
The aluminum material is obviously going to be much too flimsy. You will know just from picking it up that it is something that you will not want to stand on at all.
Try some plain steel or stainless steel material, maybe like a 4 x 4 wire mesh material?
Try Mcmaster Carr or a manufacturer like Belleville Wire Cloth:
http://www.bwire.com/
They can offer you these kinds of materials in alrge quantity at a great price. See what mcmaster carr has to offer price wise, they always go up and down with their price and availability because they are obviously a buy and sell company.
Worth a shot good luck guys.