Aliexpress
Here are coupons that you can use.
Latest price update (UTC time):
Banggood
Banggood warehouse is located in Hong Kong.
Link: Banggood product page
Coupon (192.28 USD): BGSaleFeb8
Coupon (192.28 USD): BGSaleAD
(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): BGR9T12805, 13f142, BGGutscheine, TTBLACK5, JanBGCoupon8
(I don’t think these’re gonna work, but you can try ’em out anyway)
Price history and price alert
Check out price history chart (for all/most countries) for Xiaomi Redmi 9T 4/128GB Snap662 Global.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).