Aliexpress
Click here… to search for Xiaomi Waterproof Mouse Pad 800x400x3mm on Aliexpress
Here are coupons that you can use.
Latest coupon code price check (UTC time):
Banggood
Banggood warehouse is located in China. There is no active coupon in my database right now (for 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): BGc0ac93, Cuponation9, BGKBandmos12, BG975636, BG589b2e
(sometimes old coupons work, so you can check them out (this site checks them on every price update))
Price history and price alert
Here is price history (for all/most countries) for Xiaomi Waterproof Mouse Pad 800x400x3mm.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).