It's possible to build a model for CP to reproduce much of its behavior. If you can build a 2D table from reference data for the flowrate as a function of RPM and pressure difference (head, pressure ratio, etc.), you can implement this table in Simscape to drive a controlled mass flowrate source. In this example: https://www.mathworks.com/help/hydro/ug/sscfluids_ev_thermal_management.html, the compressor is modeled using such an approach. In case of a pump, where you may be able to assume the density doesn't vary much, you can potentially simplify it by removing the non-dimensionalization with reference pressure and temperature, so the model is simpler.
Another possibility is to use the Centrifugal Pump (TL) block and the TL-2P interface. If you are working with water, this may work just fine, as the default fluids for TL and 2P are both water. The limitations of the TL-2P interface still apply though.
