You can create price alert here, copy coupons and view price history. Let’s see what best price is ATM.
Material PVC, Interface Type-C, Continuous spray time 9h, Power input DC 5V – 500mA, Humidification amount 45mL/H, Output Interface USB-C, Working frequency 108KHz, Intermittent spray time 18h, Maximum output power 2W, Capacity 400mL, Product size 148x75x134.7mm, Color Black/White, Brand SOLOVE, Model H5, Weight 256g
Aliexpress
There’re some similar (or not) items on Aliexpress
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. One coupon is available. Cool!
Link: Banggood product page
1. ($33.64): 6GSGIT
you should apply the coupon in your cart after clicking “Proceed to checkout”. Click to copy code and open shop.
Exclusive Allowance Coupons: https://bit.ly/3xWgD9k and https://couponsfromchina.com/short/5cd
Old coupons (from the oldest to the newest): BGHONEY2110, BGSHOM15, BGSHE15, 13f142, BG10OFFAFF1
(you can check these old coupons out, but these probably won’t work)
Price history and price alert
Here is price history (for all/most countries) for Youpin SOLOVE Humidifier 400ml.
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)).