Walmart offers the Intex Twin Classic Downy Airbed Mattress in Blue, model no. 68757WL, for $7.97 with free shipping. That's tied with our mention from two weeks ago (which required in-store pickup) and the lowest total price we could find today by $6. It measures 39" x 75" x 8.75".
Of note, it's also available in queen, model no. 68759WL, for $15.97 with free shipping. (Amazon has it for pennies more.) That's $4 off and the lowest total price we could find.