Costway offers its Costway 4" Twin Folding Sofa Bed Foam Mattress with Handles for $88.95. Coupon code "DNHT0988" drops the price to $74.95. With free shipping, that's $37 off list price and the best deal we could find. The mattress features high-density foam construction and a washable cover. The flat dimensions are 54" x 27.5" x 12". Note: Full and Queen sizes are also available for $96.95 and $101.95, respectively, via the above coupon code.