Get yourself a domain name. It doesn’t cost a whole lot and also allows you to complete DNS-01 challenges for SSL certs. It’s also, like, your own. That’s also a requirement for owning your email address.
(If you really don’t want to pay and don’t care about email, you can also use a shared domain DNS such as dedyn.io.)
You then simply set records to the Tailscale IP addresses of the hosts and you’re good to go. Alternatively, you can also set them to the hosts’ LAN subnet addresses and forward your subnet via a single subnet router; that’s how I do it.