Just check coupons out (with price alert and history). Do you want to know what the best price is?
Size: approx.19.7×30.7x21cm, Material: Acrylonitrile Butadiene Styrene(ABS) + Polypropylene(PP), Capacity: 4 Gallon / 15L, Battery: 2x AA Battery(Not Include), Color: White
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 Europe 
. I can’t find any active coupons for this product in Banggood. This is new product in my database, so I don’t know if this price is good.
Link: Banggood product page
Price: $-3
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!
Price history and price alert
It doesn’t make sense to generate price history chart, because there is one price record which is: $20.99.
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)).