Aliexpress
Click here… to search for Xiaomi Tinymu Replaceable Toilet Filter on Aliexpress
Here are coupons that you can use.
Latest price update (UTC time):
Banggood
Banggood warehouse is located in China. I am tired of searching coupons, but I found one for you…
Link: Banggood product page
Coupon (19.78 USD): 13f142
(CouponsFromChina.com tip: apply it in your cart 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): 8b5326, 502C6B, vipupgrade8, TTxBG10, aff7off, bgssaff9, AFfbG10, affbg10, BGBFAFF2019, BGCITYADS2019, BGHOMEG12, FBCOUPON1
(I don’t think these’re gonna work, but you can try ’em out anyway)
Price history and price alert
Here is price history (for all/most countries) for Xiaomi Tinymu Replaceable Toilet Filter.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).