Size 126x 126x 234 mm, Capacity 120ML, Weight 580g, Frog Quantity 20±5ML/H, Light Color 7 Color, Voltage / Power 24V / 12W, Applicable Area Less than 10m2.
Basically copy coupon, view price history or create e-mail price alert. Best price?
Aliexpress
There’re some similar (or not) items on Aliexpress
You can use link bot to get even lower price:
Click here to search by yourself. Here are coupons that you can use.
Latest coupon and price update (UTC):
Banggood
Banggood warehouse is located in China.
Link: Banggood product page
1. ($32.93): bgssaff9
2. ($33.66): PICODICOM
put item in your cart and apply coupon code there after clicking “Proceed to checkout”. Click to copy code and open shop.
Additional Banggood coupons: first page and second page
Old coupons (from the oldest to the newest): 502C6B, 919c60, BGDEER05
(I don’t think these’re gonna work, but you can try ’em out anyway)
Price history and price alert
Here is price history (for all/most countries) for Xiaomi Deerma DEM-XS12 Ultrasonic Humidifier. The lowest price was: $29.34.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood and Aliexpress (only if product name will be the same as on Banggood and I will post it on social media though, so it’s more like Banggood price alert)).