expanded metal lath , sold at every home building center in bare metal and gal, used primarily as underlay for ceramic tile. 3'x8' sht is about $15.00, look in the tile dept.
available in aluminum usually in the metal project aisle near the fasteners.
The stuff that looks like screen but is stiffer and has 1/8, 3/16, or 1/4 sq holes is called "hardware cloth" and sold by the foot at better building centers. Usually blk or galv finish. Its very cheap compared to a rad kit.
