iTech Deals still offers this Mesh Lumbar Back Support System for $2.99 with free shipping. That's tied with our expired mention from two days ago as the lowest total price we could find by a buck. It attaches to your chair with an elastic strap and is height adjustable.

Need more than one? Opt for the 2-pack for $4.99 with free shipping. (Select this option after clicking "Get it Now".) That's the best price we could find by $4.