Hey,
I read your requirements and I hope I understood.
You need a cookie consent pop up with accept button and you need it as independent without any third party script.
I have created the same thing for some of my projects and its working fine.
And I am ensuring you that its a independent script you can change anything, like the popup design and the message.
And the full script will be in your site, no third party.
Please contact for more discussion .
Thanks