Aliexpress
Here are coupons that you can use.
Latest price update (UTC time):
Banggood
Banggood warehouse is located in Hong Kong. I’m afraid that there’s no working coupon 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): BGOP9R128, 13f142, BG9R827, BG86bed6, BGOP9R128725, BG23124d, BGec2fd2, BGb01eca, BG80a537, BGa4da76, BG4519fd, BG15753b, BGff9107, BG5a0d0a, BGc4ee18, BGfe07d3, BGd1516a, BGcc8396, BG5c8357, BG05d4fe, BG144769, 2022ACTIESNL
(I don’t think these’re gonna work, but you can try ’em out anyway)
Price history and price alert
Here is price history (for all/most countries) for OnePlus 9R 5G 8/128GB Snap870 Global ROM.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).