class InlineCssNode(template.Node):
            ...
            if settings.DEBUG:
                expanded_path = finders.find(path)
            else:
                expanded_path = staticfiles_storage.path(path)

INLINECSS_CSS_LOADER = 'django_inlinecss.css_loaders.StaticFinderCSSLoader'

# myapp.css_loaders.py
import requests
class StaticUrlCSSLoader(BaseCSSLoader):
    def load(self, path):
        """
        Retrieve CSS contents by URL
        """
        url = staticfiles_storage.url(path)
        response = requests.get(url)
        response.raise_for_status()

        return response.content

# settings.py
INLINECSS_CSS_LOADER = 'myapp.css_loaders.StaticUrlCSSLoader'