I got an Aukey 10,000 mah from Amazon.com and another OLALA 20,000 mah and both work well.
Aukey is good, both in performance and looks, I have their USB 3.0 hubs, Luna wireless charger for my Nexus and also a travel router with battery... and none of them have failed me. Unfortunately though not available in Amazon.in.
I have a friend using the Mi power bank and he is happy with it. Ditto for the Motorola power bank.
Do note they don't charge fast... if its quick charging then a USB "dumb" charging cable via PC or laptop or a 2.1 Amp wall socket charger are better options. The power banks are better suited for idle charging when travelling in cars or airport lounges.