How can I update a GLB/GLTF 3D model texture in Python

I want to load a GLB model in Python, replace the existing texture with another texture image and save it.

So far I can load, modify and export the model. Also, I found a way to append a local image to the model. But I'm not sure how to find and replace the existing texture.

Example 3D model with one texture file: https://modelviewer.dev/shared-assets/models/Astronaut.glb

from pygltflib import GLTF2
from pygltflib.utils import ImageFormat, Image

filename = "Astronaut.glb"
gltf = GLTF2().load(filename)

image = Image()
image.uri = "new-texture.png"

gltf.images.append(image) 
gltf.convert_images(ImageFormat.DATAURI)
gltf.images[0].uri
gltf.images[0].name

# How to find and replace the existing texture?
# ...

filename2 = "updated-3D-model.glb"
gltf.save(filename2)