I have never done it, but it can be done.
You will need a compressor, evaporator, condensor, hoses. You will probably need controls to regulate the temperature.
Everything can be done, it just depends if it's worth the cost of doing it.
My S150 has AC already, but if i had one without, i'd like to fiddle to see if i could get it into one by using parts from an old car. All the parts will be matched, the only issue would be hoses, but you can get places to make them for you.