Add these two cases to your cart:
And at checkout use this code in the promotions box: W7Y7G8PQ
If you want other colors of the slim shell case you can pick those, but will require a new promo code.
Slim Shell Blue: MAZLXZI6
Slim Shell Gray: 6TBE32M9
Slim Shell Magenta: VXGBIXGO
Slim Shell Purple: SKBOHPIH
Slim Shell Red: D9ZISOBG
That'll drop the price to $9.98 including 2 day shipping if you have Amazon Prime.