Mosiso via Amazon offers Prime members the Mosiso Rubberized Case for Apple MacBook Air in Rainbow for $14.99. Coupon code "FV9U6RP7" cuts it to $9.99. With free shipping, that's the lowest total price we could find by $8. (Non-Prime members can spend $35 or more to qualify for free shipping; otherwise, shipping costs $8.41.) It's compatible with 13.3" models.