Such a program cannot exist. "Modelling" is just a catch all term. But in practice nobody learns "modelling". They just get deep in one field and learn how to m

Such a program cannot exist. "Modelling" is just a catch all term. But in practice nobody learns "modelling". They just get deep in one field and learn how to model problems in that field. Those people are often not mathematicians, but engineers working on applied problems. What you need to do is to get interested in something cool. Then contact research groups in that field and ask them if there is a place for you. You will no learn modelling. But you will be doing modelling of one very specific problem.