try mcmaster-carr (www.mcmaster.com) I think they ship internationally. look under perforated materials in the "raw materials and springs" paragraph at the bottom of the page. the cost per sheet is kinda high (US$80) but that's for a sheet almost a meter square, and stainless steel too. they offer lower grades of steel and even brass and aluminium, which are cheaper. mayhap you and a few mates could pitch in on a sheet and split it up. Mmmh, they offer a neat hexagonal pattern too... could be a good theme for a mod?
try your local metal shop, i found a sheet 2x4 meters for $28, at shoesteel, you could even try the dump
I agree with the dump idea. Also check all the random appliances you have around the house. Microwaves are a good source of mesh (just don't tell the parents/wife and stay away from the microwave while its operation!)
LOL - that stuff is like 5mm mesh - maybe even bigger if I remember. I need 1mm stuff - like on the front of my coolermaster 410 or the V1000 case.