I have checked all old coupons and price is 27.99 USD for Xiaomi 2pcs Brush (in Banggood). You can create price alert here, copy coupons and view price history. You probably want to know what is the best price?
Latest price update (UTC time):
Banggood (27.99 USD)
Banggood warehouse is located in China. Too bad there’s no coupon right now in Banggood. I think you want to know if the price is good. This price is higher than average price (24.32 USD) for this item.
Link: Banggood product page
Price: 27.99 USD
Exclusive Allowance Coupons: https://bit.ly/3xWgD9k
Old coupons (from the oldest to the newest): BG589b2e
(system checks these coupons on every price check (like once per 24 hours), but you can check them out anyway)
Aliexpress
Here are coupons that you can use.
Price history and price alert
Price history (for all/most countries) for Xiaomi 2pcs Brush Head for T700 Toothbrush is here.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).