I just found this randomly, but you can get a variety of phone cases for as little as $3.99 using Code:ANKERP399.
iPhone X
Breeze Case Soft TPU Cover Shell Black https://amzn.to/2S3hqe3
Breeze Case Soft TPU Cover Shell Golden + Black
https://amzn.to/2UZyun0
Shield Case Soft TPU Cover Black
https://amzn.to/2IgN1t9
Silicone Case Shockproof with Soft Microfiber Cushion Pink
https://amzn.to/2Gs8UUM
Touch Case Matte Finish Cover Shell Skin Black
https://amzn.to/2TVTnQh
Ice Case Hard Back Black
https://amzn.to/2Ebda8P
Shield+ Case Dual Layer Black
https://amzn.to/2S6jked
iPhone 8/7 Plus
Breeze Case Soft TPU Cover Shell Military-Grade Black
Ice Case Semi-Transparent Hard Back and Soft Bumper Black
Rise Case Hybrid Heavy-Duty with 360° Rotating Kickstand Black/Red
iPhone 8/7
Ice Case Lite Clear Cover Case with Hard Bumper Frame and Enhanced Grip Black
Breeze Case Soft TPU Cover Shell Military-Grade Certified Black
(I think these deals are still active)
Edit: Links Should be correct.