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 (41.13 USD): BGPROBuscape
Coupon (43.55 USD): BGAProjector
(CouponsFromChina.com tip: apply code in your basket (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): TECH8%, 7f09ac, BG3CSUM, BGBFAFF2019, BGCITYADS2019, 0e7f33, aff7off, FBCOUPON1, bGhOnEy10, BGdragonBoat, BGAFF7OFF, bgshOOp10, BgoFErTaSchInA10, BgcLuBofErtA10, BGAFF10OFF, 13f142, BGHONEY2110, BGProjectors
(these codes were not working in latest coupon update, but you can check them out anyway)
Price history and price alert
Do you need price history chart (for all/most countries) for Excelvan 100 Inch Projector Screen? There we go.
Price records source(s): Gearbest, Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).