Aliexpress
Here are coupons that you can use.
Latest coupon and price update (UTC):
Banggood
Banggood warehouse is located in China. We have found one coupon for this product!
Link: Banggood product page
Coupon (9.28 USD): 13f142
(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
Old coupons (from the oldest to the newest): BG9NY, BGHOMEAPP, bGhOnEy10, BGSS10%SW, bgshOOp10, BGHome15%, BGHOMEAPP13, BGHOMEA13
(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 Xiaomi Side Brush for Mijia Vacuum Cleaner 1C.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).