I have the Venture 30 recharger from Goal Zero, which I am very happy with and use when I am in the outdoors, its rugged, waterproof, has a bright LED flashlight. However, it has heft to it and not exactly pocket size.
i was looking for something small to walk around a city with with on a recent vacation and was very happy with the Anker Astro E1. I used it daily and was very pleased with it. Its small enough to fit in your pocket, light, I got multiple charges from it and its reasonably priced.
I purchased it along with this Anker PowerLine MFi certified USB cable which was also compact enough to carry in a pocket
I ordered that to replace a cable from Skiva that I would not recommend
It was convenient to have the 2 in 1 functionality of a lightening connector and micro USB connector, the problem is that they very easily separate from each other, which makes it impractical to use if you are moving around while charging your phone.