I've had one of these for about 15 years: https://www.amazon.com/Xantrex-XPower-Powerpack-Portable-Source/dp/B000E6LEIC
http://www.xantrex.com/documents/Backup-Power/powerpack-600/XPower_600HDPP(975-0213-01-01_Rev-C).pdf
I think Duracell sells the same thing under their name.
I replaced the internal battery about three years ago and it's going strong. When I bought mine, it was about $170, not $390, which is the current price on Amazon.
This unit has a capacity of 28 AH. For outlets, there is a cigarette lighter plug for 12VDC and three 120VAC outlets running through a very clean inverter (I needed clean power to run a CPAP and this unit will run mine for two nights with the humidifier off). You can also gang batteries together and I often add a 35 AH deep cycle in series.
The unit also has a radio and a light and can be used to jump start a vehicle. I only use the radio by accident
but the light is handy sometimes.
If you don't need this much power, you may be able to find something smaller, but I don't have any info about smaller units.
