Reddit mentions of Energizer XP18000 Universal AC Adapter with External Battery for Laptops, Netbooks, and More

Unfortunately, what you're suggesting (DC storage to AC intermediate "wall socket" power to DC use by the device) is a bit impractical and inefficient. Many power inverters (a device for turning DC current into AC), can have efficiencies down to 50% when you use them in a trickle mode to "top off" a battery and near 90% when you use the full rated capacity of the inverter. As well, most digital electronics use DC power internally, this AC power you just generated will have to be converted back into DC power. This process will also loss some of the energy as heat as well.

Taken together, this means that you will probably need about two to three times the amount of battery (with associated weight) to run your "universal charger".

What I would suggest would be to have a DC power source you can tie directly into your portable device without having to convert between AC and DC twice.

First: Many small portable devices will charge off of USB. USB is already DC and they make dozens of battery packs (some rechargeable) that will supply power to anything that can draw current from a USB cable. http://www.google.com/search?q=usb+battery+pack

Secondly, if you need to supply power to a portable device which cannot charge off of USB (such as a laptop), your best solution would be to buy a specific external battery/spare battery for your laptop, that you can recharge from or swap to. Most modern OSes can save their current state to the harddrive (e.g.: hibernation mode), so you can power down, swap batteries and power up in seconds.

Edit: Would something like this be what you're looking for: http://www.amazon.com/Energizer-XP18000-Universal-External-Netbooks/dp/B002K8M9HC

Something like this. There are some cheaper ones, but not many.

I've considered doing something similar with one of my battery packs. It has two DC outputs, and I did the math one night, which came out to something like 65W on the 19V output.

The intersection of small screens (14" or less), good battery life and good gaming potential isn't a very large one.

The current Razer Blade is one of the go-to choices in this range, but it's out of your budget and doesn't have a very good battery life (4 or 5 hours at most, from what I recall). The Gigabyte P34Gv2 is in your price range, but has a similarly bland battery life (6 hours idle, maybe 4 with light usage). The Clevo W230SS (sold under a few different names, including as the Sager NP7338) is much cheaper and quite powerful for a 13" laptop, but has a similar battery life. The Lenovo Y40 has a pretty good battery life (maybe 6-7 hours), but is a fair bit less powerful so probably wouldn't fit your usage very well.

Would you be willing to consider carrying around an external battery pack, something like this or this? The battery in the P34Gv2 is around 60Wh, and the one in the W230SS is around 50Wh; adding an external 150Wh battery to that would give you a pretty large improvement, though it could be a bit of a hassle to carry around an external battery.

You might look into this:

http://www.laptopmag.com/review/accessories/energizer-xp18000a.aspx

http://www.amazon.com/Energizer-XP18000-Universal-External-Netbooks/dp/B002K8M9HC

I just bought one of these, as it can also replace a laptop's power adaptor: http://www.amazon.co.uk/Energizer-XP18000-Universal-Rechargeable-External/dp/B002K8M9HC