Amazon offers Prime members the Everlast Pilates 4-Way Ab Stretch, model no. EX7661BK, for $5.83 with free shipping. (Non-members can spend $35 or more to qualify for free shipping; otherwise, it adds $5.58.) That's the lowest total price we could find by $14. It's designed to increase muscle tone, strength, and flexibility in your upper and lower body.

Note that it's expected to ship in three to six weeks.