There exists no portable air conditioning unit for cars. Your car already has the ductwork and the fusebox AC capability, but you'd need to add as a minimum a compressor, a condensor (in many cars it's a part of the radiator, in many it's a seperate small radiator), and an evaporator, as well as the control panel. The expense would kill the idea.
I have a 2000 Honda Civic that is paid off and works great. It does not have air conditioning. Is there such a thing as a portable air conditioner for car? There is a very strong chance that I will be moving from the west to east coast and will be driving across country in summer heat.