Basically copy coupon, view price history or create e-mail price alert. Do you want to know what the best price is?
IP rating: 5ATM, RAM: 16MB, Charging Time: About 60mins, ROM: 40MB, Bluetooth Version: Bluetooth 5.0, Battery Capacity: 195mAh, Screen size: 1.2 inch, Operating mode: Touch Screen, Screen resolution: 390x 390, Waterproof / Water-Resistant: Yes, Standby time: 12 days, Screen: AMOLED, Model Number: GTR
Aliexpress
There’re some similar (or not) items on Aliexpress
Click here to search by yourself. Here are coupons that you can use.
Latest coupon and price update (UTC):
Banggood
Banggood warehouse is located in Hong Kong.
Link: Banggood product page
1. ($112.49): amazfit100
2. ($119.99): 7d18f7
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 and https://couponsfromchina.com/short/5cd
Old coupons (from the oldest to the newest): BGGT42M, BGGTR42, AFfbG10, 8fbade, bggtr128, BGGTR129, BG11GTR42, BGGTR42119, BGGTR42JL, BGGTR109, BGGTR100, BGGTR11499, BGALIBUYTR, BGALIBUYAGT, Email5, BGFabioamaz
(system checks these coupons on every price check (like once per 24 hours), but you can check them out anyway)
Price history and price alert
Price history (for all/most countries) for Xiaomi Amazfit GTR 42mm Smart Watch is here.
Price records source(s): Gearbest, 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)).