Org doesn't allow external actions - can't checkout with custom checkout

The org my repo is in doesn’t allow the use of external actions in our workflows. I looked at this post (I had the same error message) and tried to copy the actions/checkout code into my repo, but then I get the following error:
“Error: Can’t find ‘action.yml’, ‘action.yaml’ or ‘Dockerfile’ under ‘/home/runner/work/repo/repo/.github/actions/checkout@main’. Did you forget to run actions/checkout before running your local action?”

I can’t add new repos in my org, so I can’t clone actions/checkout@v2 (or whichever version) into my org, so how would I do this in these circumstances?

You can use regular Git commands (think git clone, git checkout, …), but note you’ll have to select the right ref to check out. I think it might also make sense to talk to your organization admins to see if they’re willing to allow at least basic official actions (like actions/checkout).