Center City Auto Parts via eBay offers this Reusable Grill Mats 2-Pack for $6.95 with free shipping. (Or buy two for $12.50 with free shipping.) That's tied with under our mention last week and the best deal we've seen. They're also a current low by $3, excluding the below mention. They measure 15.75" x 13", are non-stick, and can be used at up to 500° F.
A close price: Amazon offers it for $7.75 with free shipping.