This is the jacket I wear.
http://www.ramweldingsupply.com/prod...ew.mcic?s=3593

I also wear an undershirt and a regular work shirt when I weld. I know it sounds crazy to weld in two shirts, but it will keep you cooler. The undershirt soaks up all the sweat while the work shirt stays dry. It traps air along with the sweat keeps you cooler.