Back-up manual tongue jack

My husband is nervous about trailering because he's not mechanically inclined and fears trouble that he can't fix. So the issue of relying on the electric jack came up. I'm wondering if there is such a thing as a manual crank that can be used on a normally electric crank, just in case. Belt and suspenders, that's me. He's concerned about the battery running down and us not being able to hitch up or unhitch.

So is there such a thing as a manual crank for the jack?