Product size: 108*68.8*24.2mm, Rated capacity: 5800mAh (5V/4A), Power (W): 50W MAX, Material: ABS, about 3.2 hours (18W charger), Model: PB1050ZM, Input: 5V-3A/9V-2.7A/12V-2A/15V-1.6A/20V-1.2A, Output: 50W MAX, Charging time: about 5 hours (5V/2A charger), Working temperature: 5 – 35 Deg.C, USB-A (single port): 5V-3A/9V-3A/12V-2.25A/20V-1.35A, Type: Portable Mobile Powers, USB-C: 5V-3A/9V-3A/10V-5A/2V-3A/15V-3A/20V-2A.
Just check coupons out (with price alert and history). Best price?
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.
Latest coupon and price update (UTC):
Banggood
Banggood warehouse is located in China. We have found one coupon for this product!
Link: Banggood product page
1. ($76.61): BG85d5c6
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/i1u
Old coupons (from the oldest to the newest): BGXMI15, BGdragonBoat, BGSS10%SW, BGAFF10OFF, bgshOOp10, BgoFErTaSchInA10, 7d18f7, BgcLuBofErtA10, BG15POWERBANK, BGCuponation10, 13f142, BGHONEY2110, BANGGOODSD, BGCCARG
(probably won’t work, but you can try them out)
Price history and price alert
Here is price history (for all/most countries) for Xiaomi Power Bank 3 10000mAh 50W PB1050ZM. The lowest price was: $46.99.
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)).