mmm I'm afraid you can't, each browser vendor subscribe the serviceWorkers to its own Message Server (Chrome: fcm.googleapi.com, Firefox: updates.push.services.mozilla.com, etc.), so it is something we don't have control over...
Although technically there's a solution, it would require you to sort of "hack" your network, namelly, it would require a Man In The Middle attack. You would have to code a program to redirect all your network traffic to that program (probably using raw sockets, and sending ARP packets), and then make that program listen for request to those Message Servers (those request will be over HTTPS - port 443), then your program has to send exactly the same response the real Message Server would send. It's is not an easy task.... but it is the only solution I cant think of.
Note: Your browser will block any serviceWorker registration that is not over a "secure connection", that means that your server MUST be serving request over HTTPS or you could install your web app locally on your users devices (so that they can be accessed by "localhost").