I followed duydb's answer to produce the python code below that automates this process.
import requests
with open("example.css", "r") as f:
text = f.read()
urls = re.findall(r'(https?://[^\)]+)', text)
for url in urls:
filename = url.split("/")[-1]
r = requests.get(url)
with open("./fonts/" + filename, "wb") as f:
f.write(r.content)
text = text.replace(url, "/fonts/" + filename)
with open("example.css", "w") as f:
f.write(text)
Hope this helps with some of the copy-paste death.