Best sources I have found for the stainless steel wire mesh material are the following and all can be ordered online, without too much hassle.
www.mcmaster.com
www.grainger.com
http://www.bwire.com/index.html
One lesson I have learned the hard way over the past few years - always search around for the best pricing on this material! Prices can vary by about 50 % in either direction depending on what place you buy from! DO YOUR RESEARCH!