Basically copy coupon, view price history or create e-mail price alert. You probably want to know what is the best price?
12x Side Brushes, 1x Cleaning Tool, 1x Main Brush Cover, 0.3kg, ABS, Vacuum Cleaner Parts, 6x HEPA Filters, 1x Main Brush, Xiaomi Mijia STYTJ02YM MOP PRO Vacuum Cleaner
Aliexpress
There’re some similar (or not) items on Aliexpress
Click here to search by yourself. Here are coupons that you can use.
Latest price update (UTC time):
Banggood
Banggood warehouse is located in China. I’m afraid that there’s no working coupon in Banggood.
Link: Banggood product page
Price: $-3
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 and https://couponsfromchina.com/short/5cd
Old coupons (from the oldest to the newest): BGCNFDSC, BG10OFFAFF1, BANGGOODSD
(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 21pcs Replacements for STYTJ02YM MOP PRO Vacuum Cleaner.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood and Aliexpress (only if product name will be the same as on Banggood and I will post it on social media though, so it’s more like Banggood price alert)).