I have a Dell, I think it is the D400. It has an extra battery that plugs under the PC. The size of the footprint of the battery is the same as with the laptop. It gives me 6 to 8 hours of operating time which is great for long flights etc. It comes with a high-power charger although you can use the regular as well (but with longer charging time). The combination gets a bit high for desktop use but that hasn't bothered me on the plane or in the lounges where tables are often low. I realize the Dell is not what you are looking for, but maybe there's a similar setup available for your computer.