Good answers aplenty already from my colleagues.

1 thing I'd emphasize is this: You won't FIND a ready-made solution using existing resources. No, you must INVENT your brand and test it on people.

If you can watch them being persuaded while you say the tagline or give the pitch, then it works. Browsing online won't tell you that. Talking to people will.

Suppose you were writing a story. You wouldn't ask for the "best resources to find the perfect opening sentence". That's crazy! Such things aren't out there to be found. They're made.

So my advice is ... If you're stuck, hire a pro. Once you have a pitch and a tag line, try them out and see if they feel effective.