Aliexpress
Here are coupons that you can use.
Latest price update (UTC time):
Banggood
Banggood warehouse is located in China. Only one coupon available!
Link: Banggood product page
Coupon (9.39 USD): BG00c906
(CouponsFromChina.com tip: apply it 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): 2203ActiesNL
(there’s a little possibility that old coupon will work)
Price history and price alert
Here is price history (for all/most countries) for OPEN-SMART 2.8 inch TFT LCD Display.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).