You won't find a real pumping unit this small. I've seen some training models that were 2-3 ft tall, but they weren't functional. The smallest I've personally seen was, I believe, a C25 & it was about 5 ft tall. Lufkin has a used pump center. You can contact them ...
Not sure what kind of expiriments you are planning, but about the smallest pumpjack you will find is an old water well pumping unit, a Jensen Brothers Pump jack would be in your size range, there is one for sale on Ebay currently