You can create price alert here, copy coupons and view price history. What is best price?
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):
2x Tool Brush, 4x Slide Brush, 2x Main Brush, 4x Fliter
Banggood
Banggood warehouse is located in China.
Link: Banggood product page
1. ($16.06): BGAFF10OFF
2. ($16.06): bGhOnEy10
you should apply the coupon in your cart after clicking “Proceed to checkout”. Click to copy code and open shop.
Exclusive Allowance Coupons: https://bit.ly/3xWgD9k and https://couponsfromchina.com/short/5cd
Old coupons (from the oldest to the newest): BGXMF11, TA12, BGAT18, BG2020NS
(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 12Pcs Mi Robot Vacuum Cleaner Accessories.
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)).