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 (128.09 USD): BGPROBuscape
Coupon (135.62 USD): BGAProjector
(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): BGCheerC91, BGPAYPALSS, aff7off, BGaDmITAd, bgchinafest, BGBFAFF2019, BGCITYADS2019, bGpAnDacHeCk, BGMPB2020, Email5, bGhOnEy10, BGdragonBoat, BGAFF7OFF, bgshOOp10, BgoFErTaSchInA10, 7bcdf9, BGProjectors
(there’s a little possibility that old coupon will work)
Price history and price alert
Check out price history chart (for all/most countries) for Cheerlux C9 Projector.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).