I have just got one of the Ongnuo External battery Battery packs for my speedlights, Cost me 46 for next day delivery from within the UK. I know there cheaper if you get them shipped from China or Hong Kong but I wanted to be able to send it back without any problems if it was faulty. It isn't and it seems as good as the Nikon one which sells for something silly like 180, have to confess to having bought one before I discovered these.
Anyway can certainly recommend ukhighlandphoto. A friend has one for his Canon guns and is also very pleased with it.
Ebay link is