$20.99 – Frame Material Nylon+Stainless Ssteel, Model TYJ04TS, Size 60X14X150MM, Weight 19g(approx.), Color Gradient Grey.
You can get Xiaomi Mijia TYJ04TS Sunglasses Pro Pilot for $20.99 with coupon (from Banggood). Basically copy coupon, view price history or create e-mail price alert. Let’s see what best price is ATM.
Latest coupon and price update (UTC):
Banggood ($20.99)
Banggood warehouse is located in China. There is no active coupon in my database right now (for Banggood). The question is – is it a good price? It’s a good price, isn’t it? The average is $21.53.
Link: Banggood product page
Price: $20.99
Additional Banggood coupons: first page and second page
Old coupons (from the oldest to the newest): Brand2, vipupgrade8, BGHECARE1, BGXPMA1002, BG4ee866, BGafeb99, BGba6851, BGHUXC032, BGcb3482, BGa6a3d1, BG8ReviTrage, BGd2b99b, BG8ee8e5, Cuponation9, BG63a223, 9OFFSUMMER, BGba6b4c, BG75597c, BG33a4cd, BG6b7360, BG5a65f5, BG3147f9, BGTYXMG2, BGTYXMG4, BGTYXIMI, BGSEPXIMI, BGNOVE6, BGCYCLE5
(probably won’t work, but you can try them out)
Aliexpress
There’re some similar (or not) items on Aliexpress
You can use link bot to get even lower price:
Click here to search by yourself. Here are coupons that you can use.
Price history and price alert
Price history (for all/most countries) for Xiaomi Mijia TYJ04TS Sunglasses Pro Pilot is here. The lowest price was: $18.99.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood and Aliexpress (only if product name will be the same as on Banggood and I will post it on social media though, so it’s more like Banggood price alert)).