Just check coupons out (with price alert and history). Best price?
Card Extend: Supports an external TF card up to 256GB (VFAT), , GPU: Mali G57 / up to 950MHz, CPU: MediaTek Dimensity 700 Octa Core / up to 2.2GHz, ROM: 128GB UFS 2.2, OS: MIUI 12 for POCO / based on Android 11, RAM: 6GB LPDDR4X
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. Too bad there’s no coupon right now in Banggood.
Link: Banggood product page
Price: $-3
It looks like this item is out of stock in Banggood. If you found it then please send me the link. I will replace it.
Click here to search on Banggood!
Exclusive Allowance Coupons: https://bit.ly/3xWgD9k and https://couponsfromchina.com/short/5cd
Old coupons (from the oldest to the newest): 13f142, BGEDM3P, BGEUM3P, BG42ad1e, BG3e16b7, BGdb8c91, BGd3ce35, BG15b591, BGc3557a, BG44df9d, 2022ACTIESNL, BG78f477, BG1fae9d, Terence, BG5153a6, 8BGwbg2204, BG804c3a, BGb897de, BGc0024f, BGROTTERG3, BGaa88f0, BG9f5d3e
(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
Here is price history (for all/most countries) for POCO M3 Pro 5G NFC 6/128GB Global.
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)).