You can keep a copy of its state_dict(). This should work:
from collections import OrderedDict
best_model_state_dict = {k:v.to('cpu') for k, v in model.state_dict().items()}
best_model_state_dict = OrderedDict(best_model_state_dict)

Later, you will be able to load that model by doing model.load_state_dict(best_model_state_dict)