Couldn’t you just get a regular domain and use a firewall to prevent access, so only your IP address(s) are able to access it.

I’m currently doing this myself, however I have a VPN on my local network that allows me access to my self-hosted service remotely as if I was at home.

There are other things you can do with cloudflare that will lock the sites down with authentication, but VPN and firewall have worked pretty well for my use cases.