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 (16.79 USD): 915111
Coupon (22.39 USD): 5d1b0b
Coupon (23.79 USD): e2bcea
Coupon (23.79 USD): 502C6B
(CouponsFromChina.com tip: coupon code has to be applied in shop’s cart after clicking “Proceed to checkout”. Click to copy code and open shop)
Exclusive Allowance Coupons: https://bit.ly/3xWgD9k
Price history and price alert
Here is price history (for all/most countries) for HP M300 Mouse.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).