Aliexpress
Here are coupons that you can use.
Latest price update (UTC time):
Banggood
Banggood warehouse is located in China. There is one coupon available! Pretty cool, huh?
Link: Banggood product page
Coupon (44.49 USD): vipupgrade8
(CouponsFromChina.com tip: paste coupon code in your cart and click Apply 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): 20b8dc, HHHHHOT, healthylifestyle, c20360, b884b7, ML15%Pro, BGEC20OFF
(you can check these old coupons out, but these probably won’t work)
Price history and price alert
Price history (for all/most countries) for Xiaomi Custom-made TS Sunglasses for Travelers is here.
Price records source(s): Gearbest, Banggood
Click on image to enlarge. 
You can set price alert (for Banggood).