PowerStream Universal lithium ion battery pack
- Weighs 1 lb.
- Costs around $220.
- (44Watt/hr equates to 3.6 AmpHours @ 12volts)
I don't own one of these... yet 
... but it looks like a sleek little unit with built in charger, very flexible voltage output settings (5v, 6v, 7.5v, 9v, 12v, 14v, 16v, 19v) usb port, battery level meter, many different barrel plug adapters. Charging voltage can be between 5 volts and 24 volts DC or use supplied AC charger.
Since this pack is lithium ion it delivers consistently throughout its discharge until it just stops.
If you are highly mobile then this looks like a good portable battery pack that you might couple with one of the (5, 10, or 20watt) Powerfilm fexible solar panels. The 10 watt model could probably charge the pack completely in 4.4 hours, giving you one of these 44watt/hrs charges a day and still be highly portable.