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 (469.19 USD): BGSaleFeb8
Coupon (469.19 USD): BGSaleAD
Coupon (479.39 USD): BG589b2e
(CouponsFromChina.com tip: coupon code has to be applied in shop’s 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): BGProj
(there’s a little possibility that old coupon will work)
Price history and price alert
Do you need price history chart (for all/most countries) for Mijia DLP Projector Youth Edition 2 Projector with Xiaomi TV Stick? There we go.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).