helm-puller

pulls all helm images and compresses into tar.gz

cloning:

git clone https://github.com/zfrhv/helm-puller.git
cd helm-puller

helm pull <repository>/<chart>
./1#pull-and-compress.sh

take the new to-take-.tar.gz to the restricted network (using usb or any media)

push all images + helm chart to the repository:

# untar the file
tar -xzvf to-take-<chart>.tar.gz && rm -f to-take-<chart>.tar.gz

cd to-take-<chart>
vim 0#conf.sh
  
./2#extract-and-push.sh

helm repo add grafana https://grafana.github.io/helm-charts
helm pull grafana/grafana
./1#pull-and-compress.sh

this tool uses yq, make sure to install it.
this script uses podman, I can also make it work with docker but only if anyone will need it (just open an issue)