Aliexpress
Click here… to search for KZ Earphone Square PU Case on Aliexpress
Here are coupons that you can use.
Latest coupon code price check (UTC time):
Banggood
Banggood warehouse is located in China.
Link: Banggood product page
Coupon (3.20 USD): EARSP11
Coupon (3.31 USD): aff7off
(CouponsFromChina.com tip: just apply this code in your cart after clicking “Proceed to checkout”. Click to copy code and open shop)
Exclusive Allowance Coupons: https://bit.ly/3xWgD9k
Old coupons (from the oldest to the newest): e2bcea, TTxBG10, BGVDay10%off
(probably won’t work, but you can try them out)
Price history and price alert
Here is price history (for all/most countries) for KZ Earphone Square PU Case.
Price records source(s): Gearbest, Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).