iPhone external battery pack - Taipei

Looking for an iPhone 4s compatible external battery pack in Taipei.
Checked around many junk shops in Ximending and Daan, but I need it by Sunday so time to get serious with the search.

Could be a rechargeable brick or just something that uses AA batteries.

GuangHua Digital Plaza I would guess has a lot of stuff like this:



Should be able to find what you’re looking for.