Peel & Seal is a brand name. If you ask for it by name you may get blank stares. Any Home Depot has an equivalent, but it may be by a different vendor. The stores in my area have a brand called Quick Roof, in 6" wide rolls. Dunno if it's exactly the same or not.
Ask for self-adhesive roll roofing material, asphalt based with an aluminum outer skin. The roofing dude will know what you're looking for.