I am insulating a stud wall running parallel to a chimney. There is a 2" air gap between the studs and chimney. I would like to use a product that is effective at elevated temperatures. Rock wool or mineral wool have been suggested but I can't seem to find where to buy it. Does it come in batts like fiberglass insulation? I found 2'X4' rigid mineral wool panels..can that be used? Thanks in advance for your time.