You can still using the pretrained weights, here’s some code:
import torch
import torch.utils.model_zoo as model_zoo
from torchvision.models.vgg import VGG, make_layers, cfg, vgg16

class MyVgg(VGG):

    def __init__(self):
        super().__init__(make_layers(cfg['D']))

    def forward(self, x):
        # here, implement the forward function, keep the feature maps you like
        # and return them
        pass

model = MyVgg()
model.load_state_dict(model_zoo.load_url('https://download.pytorch.org/models/vgg16-397923af.pth'), strict=True)
model(torch.rand(1, 3, 224, 224))