Aliexpress
Click here… to search for HKC GF40 23.6 inch Curved Monitor 1800R 4ms 144Hz VA 1080P on Aliexpress
Here are coupons that you can use.
Latest coupon and price update (UTC):
Banggood
Banggood warehouse is located in China.
Link: Banggood product page
Coupon (252.99 USD): 8Couponsde
Coupon (252.99 USD): MVC8SPRING
Coupon (252.99 USD): 8BGwbg2204
Coupon (255.74 USD): 2203ActiesNL
Coupon (258.49 USD): BG00c906
(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): 13f142, 6GSGIT, BGPROJEKTOR, 2022ACTIESNL, Terence, Tabby20, BG1efeb0
(these coupons are old, so probably won’t work)
Price history and price alert
Check out price history chart (for all/most countries) for HKC GF40 23.6 inch Curved Monitor 1800R 4ms 144Hz VA 1080P.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).