Basically copy coupon, view price history or create e-mail price alert. Let’s see what best price is ATM.
RAM: 6GB/8GB LPDDR4X, GPU: Mali-G57, OS: MIUI 13 for POCO / based on Android 11, CPU: MediaTek Helio G96 Octa Core / up to 2.05GHz, Card Extend: Supports an external TF card up to 1TB (VFAT), ROM: 128/256GB UFS 2.2
Aliexpress
There’re some similar (or not) items on Aliexpress
Click here to search by yourself. Here are coupons that you can use.
Latest price update (UTC time):
Banggood
Banggood warehouse is located in Hong Kong. Well, there is one coupon available right now.
Link: Banggood product page
1. ($184.00): BGf8f0a0
put item in your cart and apply coupon code there 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): Terence, Tabby20, BG80a17d, BGa71544, BGc571a6, BGdd7800, BGb05cb8, BG880bef
(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 POCO M4 Pro 4G 6/128GB is here.
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)).