Making a CO2 laser portable is actually very straight forward. The one thing that would make it easier is to find an air cooled tube as opposed to water cooled. Once located you can build the tube into whatever portable form you want such as a rifle setup or what have you. You then could use a step up transformer such as a TV flyback fed by some power transistors set up to oscillate to boost your battery voltage up to the 6,000 or so working volts you need. Rectify the high frequency, high voltage current to provide a decent quasi-DC and your ready with the working voltage system. Build a capacitive booster or a voltage doubler circuit to provide the trigger voltage, 10,000 or so, from the same service. Your batteries could be 6volt or 12 volt wet cells or gel cells and the inverter circuit would be relatively small. Small enough anyway to fit in a shoulder bag. Cable between the laser head and the power supply and viola, portable CO2 laser. You would provide a working voltage feed, a trigger voltage feed, and a 12V DC feed for fans, lamps, etc. The current requirements for an operating CO2 laser are very small.
The one Aseras took apart reached 2.9W.