Aliexpress
Here are coupons that you can use.
Latest coupon code price check (UTC time):
Banggood
Banggood warehouse is located in China. There is one great coupon!
Link: Banggood product page
Coupon (17.18 USD): BANGGOODSD
(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): BGHHWED, bgssaff9, aff7off, BG6PCS, BGaDmITAd, 13f142, BGBFAFF2019, BGCITYADS2019, 2020CNY, BGVDay10%off, BGHOMEAPP, BGMPB2020, bGhOnEy10, BGSS10%SW, bgshOOp10, BGHome15%, BGHOMEAPP13, BGHOMEA13, BG10OFFAFF, BGwhielabel, BG10OFFAFF1
(sometimes old coupons work, so you can check them out (this site checks them on every price update))
Price history and price alert
Price history (for all/most countries) for 6Pcs Parts For Xiaomi Vacuum Robot is here.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).