Aliexpress
Here are coupons that you can use.
Latest price update (UTC time):
Banggood
Banggood warehouse is located in China. Coupons for Xiaomi Yeelight YLSD01YL Downlight? Nope, there’re no coupons in Banggood.
Link: Banggood product page
Price: -3 USD
It looks like this item is out of stock in Banggood. If you found it then please send me the link. I will replace it.
Click here to search on Banggood!
Exclusive Allowance Coupons: https://bit.ly/3xWgD9k
Old coupons (from the oldest to the newest): TTxBG10, aff7off, AFfbG10, BGaDmITAd, BGYLSD01YL, bgchinafest, BGYEE11COU, 13f142, BGVDay10%off, BGLIGHT2020, bGhOnEy10, BGYEE20COUPON, bgshOOp10, BGLIGHT0920, BgoFErTaSchInA10, BGELIG0920
(probably won’t work, but you can try them out)
Price history and price alert
Check out price history chart (for all/most countries) for Xiaomi Yeelight YLSD01YL Downlight.
Price records source(s): Gearbest, Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).