I got a tooth protector (the kind that's used for boxing) on amazon with a self-mold: you return it to the company that makes the final plastic thingie for you.

That'd be the preferred option, as it doesn't require any prescription or interaction with a specialist whose interest might not be aligned with the patients (multiple office visits = an opportunity to milk the insurance for more money)

If no company offers an option, I see an opportunity there!