Cassnova via Amazon offers Prime members the Cassnova 13.3" Denim Laptop Sleeve for $22.99. Coupon code "XMASOFF5" cuts the price to $17.99. With free shipping, that's $18 off and the lowest total price we could find. (Non-members can spend $35 to qualify for free shipping; otherwise, it adds $8.48.) It features a fully padded fleece interior.
Orders placed by December 19 are guaranteed to arrive by Christmas.