You can take a look at lru_cache_cache_info in Modules/_functoolsmodule.c for an example of namedtuple instantiation in C code. But that code gets the namedtuple class as a parameter.

This is not my area of expertise, but you could try using PyObject_CallFunction to call the Python collections.namedtuple function, keep the result as a module attribute, and then call that whenever you want to create an instance.