Aliexpress
Here are coupons that you can use.
Latest coupon and price update (UTC):
Banggood
Banggood warehouse is located in China. So I have checked for active coupons (all category coupons and old ones), but there was 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): BG7638, BGHONEY2110, BG10OFFAFF, BGCN6380, BGMAY084, BGwhielabel, BGjuly40, 13f142, BGjuly42, BGe258f, BGxm199a, BGxmgla77, BG10OFFAFF1, BG359fc0, BGf0a477, BGb1cbb7, BGd874e1, 00c906, BGXPJA171, BGHealth10D, 2022ACTIESNL, BGXPFE912, BGHB218, BGXPMA146, BGXPAP84, BGGRAP11, tRaDetRaCKeR, BGHECARE1, BG4ee866, BGaca9f2, BGHOM010, BG162211, Cuponation9, BG75597c
(probably won’t work, but you can try them out)
Price history and price alert
Here is price history (for all/most countries) for Xiaomi Classic Frame Sunglasses Pro.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).