Groupon offers the Sporto Women's Sport Thong Sandals in Black/Pink or Black/Teal for $7.63. Coupon code "SAVE10" makes them free. With $3.99 for shipping, that's the lowest total price we could find by $17. They're available in sizes 6 to 10. Coupon expires December 31.
Note: They're not guaranteed for delivery by Christmas.