EBay 18650 USB Power Bank
This is a great little power bank powered by four 18750 cells, giving it an approximate capacity of around 8000mAh it's capable of quite high drain and also fairly fast charging.
The aluminium case is very solid and there's two versions, both with and without a built-in lamp. The lamps around a watts-worth of white LED's, which make for a useful work light and perfect for lighting a small tent.
Described on eBay as: 5V 2A/1A Mobile Power Supply USB 18650 Battery Charger aluminum/LED lamp
I purchased from the following seller; http://myworld.ebay.co.uk/frank-studio*
The cells do not come with the case and you need to use non-protected 18650's so the chargers built in circuitry does protection of the cells. I used Deal Extreme to source the cells (as usual) and went for two packs of this SKU: http://dx.com/p/12397?Utm_rid=65939668&Utm_source=affiliate