Just check coupons out (with price alert and history). You probably want to know what is the best price?
Charging Type: Dock charging, Sensor G-sensor, Standby Time: About 504 hours, Display Size: 1.91 Inch, SIM Card: eSIM, Heart Rate Sensor, Resolution: 402x 476 pixels, Type: AMOLED, GPS: Support, WiFi: Support, Charging Time: About 1.25hours, Battery Battery Capacity: 430mAh, CPU Quad-core 1.2 GHz Cortex-A7, Internal 1GB+8GB, Network Frequency: 2G/3G/4G, Using time: About 40 hours
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 code price check (UTC time):
Banggood
Banggood warehouse is located in China. One coupon is available. Cool!
Link: Banggood product page
1. ($477.12): BG51f436
apply it in your cart 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): BGOPPOW, bgwp, Email5, 13f142, BGSWATCH10, 6GSGIT
(sometimes old coupons work, so you can check them out (this site checks them on every price update))
Price history and price alert
Check out price history chart (for all/most countries) for OPPO Watch 46mm Smart Watch CN.
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)).