Basically copy coupon, view price history or create e-mail price alert. Let’s see what best price is ATM.
Input: 100 – 240V AC., Output: 5V 2000mA
Aliexpress
I could not find it on Aliexpress. Click here to search by yourself.
Here are coupons that you can use.
Latest coupon and price update (UTC):
Price history and price alert
Check out price history chart (for all/most countries) for HN-528i AC / DC 5V 2A Power Adapter for Raspberry Pi.
Price records source(s): Gearbest
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)).