It feels as if there should be a PaaS alternative to hosting your own PyPI server (and I would gladly pay for one) but alternatives like AWS CodeArtifact require a lot of manual configuration. JFrog have the closest service that I can find, but you have to subscribe to their whole CI.
I was hoping that GitHub Packages would solve this issue (as they do for NPM, Docker etc.) but sadly this isn't going to happen.