Aliexpress
Here are coupons that you can use.
Latest price update (UTC time):
Banggood
Banggood warehouse is located in China. Only one coupon available!
Link: Banggood product page
Coupon (250.97 USD): BG589b2e
(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): BGProj, BG00d891, BGSaleFeb8, BGSaleAD, BGMARCHSALE
(sometimes old coupons work, so you can check them out (this site checks them on every price update))
Price history and price alert
Check out price history chart (for all/most countries) for XNANO X1 Projector 1080p 2/16GB.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).