Aliexpress
Here are coupons that you can use.
Latest price update (UTC time):
Banggood
Banggood warehouse is located in China.
Link: Banggood product page
Coupon (84.63 USD): tRaDetRaCKeR
Coupon (84.63 USD): 8wEbgaInS5
Coupon (84.63 USD): pROMo8cuPoN
(CouponsFromChina.com tip: just apply this code 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): BG1efeb0, MVC8SPRING, 8BGwbg2204
(these coupons are old, so probably won’t work)
Price history and price alert
Price history (for all/most countries) for Creality 3D SL1 Resin Curing Machine 405nm is here.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).