Here are a few links that I've found during my research.

This other thread contains an endorsement of the Solio Hybrid 1000.

This hand-crank product page has a comment that mentions the N810.

Still, I wonder how the hand-crank chargers work exactly. It says that you can wind for 2-3 minutes and then charge for 8 minutes. If you want to give a tablet a full charge, how long would you need to wind for? How long would it take to fully charge the battery that is built into the hand-crank charger? If you fully charged that, would it give you any indication that subsequent winding would be wasted?