I’m looking to replace these devices with something more robust. The simplest and cheapest solution to demonstrate the relationship between pressure area and force is to connect two differently sized plastic syringes and alternately press each of the plungers. A big syringe is hard to push (big area/high force) and doesn't move very far and a little syringe is easy to push (small area/low force) and moves a long way.
The problem with this approach is the amount of force required to overcome the friction from the rubber seals of the syringes. One of the reasons the calibrators leak all the time is the technical difficulty in creating a watertight seal between moving surfaces that is close to frictionless. The friction force does not contribute to the pressure in the fluid and is difficult to determine for a quantified analysis of the force/pressure/area relationship.
How critical is it for students to perform a numerical analysis after an experiment? As engineering educators who design experiments for engineering students, our default thought process is to consider the mathematical model that describes a system and figure out how to instrument our set up to demonstrate the physics. Because of this, most engineering students will do numerical post processing of their experiments ad nauseam as they progress through their diet of experimental activities in their particular programme.
Data analysis is one skill students should demonstrate they can deploy. However, there are other skills that are equally important for engineers to be able to demonstrate, such as identification of underlying principles and articulating these to others. Maybe I can simply provide the big and small connected syringes and ask student to qualify, rather than quantify the results.