CO2 stores as a liquid at a pressure of about 60 atm and a density slightly greater than water, so 1 kg would be about 1 liter. A 2.5 lb CO2 cylinder is used for dispensing beer and is fairly common. Smaller ones are also available. You will need a hand shutoff valve and one solenoid valve...
Karl--
You have two problems: rotation and translation. Your suggestion to use a flywheel, called a momentum wheel for spacecraft (see http://www.answers.com/topic/momentum-wheel) is a good one. Spacecraft use very high RPM to save mass. You could use a heavy one with a reversible motor...
I have been following the discussion and wish to put in a vote against the ducted fans, for the reason that they are hard to turn on and off quickly. With the air table, the vehicle will have very low friction. Docking requires a delicate combination of thrust times time applied in a certain...