I bought the official one. It's nice
I figured it was a little expensive in comparison to others, but agree it seems nice....
I use the TeckNet iEP387 7000mAh Dual-Port 2.1Amp.
I get about 4 times the battery life on my Vita when using it and can charge my phone at the same time. It can also charge via micro USB which has proven to be an absolutely invaluable feature most larger packs miss out on (charge from laptops, use universal USB chargers in other countries etc).
With most chargers you need to get a USB cable that bridges the D+ and D- connections, but I just made up my own mini extender that bridged them.
This is one of the units I have looked at, but I don't really want to (or have the skills) be fiddling round with cables - kinda just want to buy one that works from the off....
So, can you not just chuck in the regular Vita USB cable with this ?