In its simplest form, I think a rod pump can be conceptualized as a single-acting cylinder with two check valves. One check valve opens to extract fluid from the inlet reservoir, and the other allows fluid in the cylinder to leave in the down stroke.
You may use the Isothermal Liquid domain (recommended if you have access to R2020a or later) or the Hydraulic domain for your model. Simscape Fluids library will be required. Links to useful blocks:
