Aliexpress
Here are coupons that you can use.
Latest price update (UTC time):
Banggood
Banggood warehouse is located in China. Too bad there’s no coupon right now in Banggood.
Link: Banggood product page
Price: -3 USD
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
Old coupons (from the oldest to the newest): BG11SHOP, BGONEZ01, 7d18f7, BG45509, BGZUZUBZ, BG4BW25, BGLOAC1, BGBUDSZ27, 13f142, BGZHTOP2, BGa0b145
(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 OnePlus Buds Z Earphones.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).