Aliexpress
Click here… to search for Xiaomi Youpin MIIIW Smart Mouse Pad on Aliexpress
Here are coupons that you can use.
Latest coupon and price update (UTC):
Banggood
Banggood warehouse is located in China.
Link: Banggood product page
Coupon (56.03 USD): BGAFF10OFF
Coupon (56.03 USD): bGhOnEy10
Coupon (56.03 USD): BGdragonBoat
Coupon (57.26 USD): 7d18f7
(CouponsFromChina.com tip: put item in your cart and apply coupon code there after clicking “Proceed to checkout”. Click to copy code and open shop)
Old coupons (from the oldest to the newest): e2bcea, TTxBG10, e18b44, BGss506, BG3CSUM, AFfbG10, 502C6B, BGBFAFF2019, BGCITYADS2019, BGVDay10%off, 2880c7, BGSS10%SW, bgshOOp10, BgoFErTaSchInA10
(these coupons are old, so probably won’t work)
Price history and price alert
Price history (for all/most countries) for Xiaomi Youpin MIIIW Smart Mouse Pad is here.
Price records source(s): Gearbest, Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).