Aliexpress
Here are coupons that you can use.
Latest price update (UTC time):
Banggood
Banggood warehouse is located in China.
Link: Banggood product page
Coupon (29.69 USD): bGhOnEy10
Coupon (29.69 USD): BGSS10%SW
Coupon (29.69 USD): bgshOOp10
(CouponsFromChina.com tip: paste coupon code in your cart and click Apply after clicking “Proceed to checkout”. Click to copy code and open shop)
Exclusive Allowance Coupons: https://bit.ly/3xWgD9k
Old coupons (from the oldest to the newest): 3999KF, 35Knife, fbd8b3, Alibuy299, anydeals299, alibuy92152, 502C6B, Huohou288, xiaomiknife6, 805a35, 1964CODE, 615ac6, 4b2344, BBKK28, 2282CODE, BGK2799, TTxBG10, BG2755ck, 2019SPEDM, BG4c59ac, bgssaff9, BGblack25, BGBlack25, BGKT3566, AFfbG10, BG5131, BGBINKUPON583, bGpAnDacHeCk, BGKH92, BGTH266, BGdragonBoat
(there’s a little possibility that old coupon will work)
Price history and price alert
Check out price history chart (for all/most countries) for Xiaomi Mijia Non-Stick Slicing and Chef Knife.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).