Aliexpress
Click here… to search for Baseus Humidifier 600ml on Aliexpress
Here are coupons that you can use.
Latest coupon code price check (UTC time):
Banggood
Banggood warehouse is located in China. I am tired of searching coupons, but I found one for you…
Link: Banggood product page
Coupon (28.22 USD): 6GSGIT
(CouponsFromChina.com tip: this code has to be applied in your cart after clicking “Proceed to checkout”. Click to copy code and open shop)
Old coupons (from the oldest to the newest): BGBESHUM, PICODICOM, BGBESH, bGpAnDacHeCk, BGBSHUM, BGHOMEAPP, bGhOnEy10, 13f142, BGSS10%SW, BGBSPHUM, bgshOOp10, BGHome15%, BGHOMEAPP13, a8be6c, BGHOMEA13, BGCuponation10, BG10OFFAFF, BGwhielabel, BG10OFFAFF1
(these coupons are old, so probably won’t work)
Price history and price alert
Price history (for all/most countries) for Baseus Humidifier 600ml is here.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).