You already have one. It’s built into you. How do you think you’re able to conceive of alternative timelines and histories that that exist in the neverwas?
Time travel is so common, we laugh at it. “Just imagination”.
Just? That’s where all the power is and where all human creations start. There’s nothing a practical as imagination, by whatever name you give our abilities.
China’s banned it. (outward expression of time travel – alternate universes and such) They know how powerful it is.