Well, that’s an interesting statement to make about courses that tend to be interdisciplinary by nature.
As an example, seems the only undergrad requirement for the MPP at Georgetown is a principles of microeconomics course, and they give some options for those who have not yet done one at undergrad https://mccourt.georgetown.edu/admissions/application-requirements/program-prerequisites/
As another example Harvard doesn’t care about major but just wants to see some quantitative work done at undergrad https://www.hks.harvard.edu/admissions-aid/masters-program-admissions/how-apply/degree-program-prerequisites
In any case there seem to be plenty of undergrad options, which is what OP was asking.