[wpietri]

A more practical approach might be a way to stop water from going into the bowl. E.g., you lift up on the handle to close the tank flap. Or maybe there's a stop button next to the flush button.

That would be almost as good as an overflow drain, but wouldn't require adding second sewer pipe.

[maxerickson]

A solid linkage between the handle and flap is available.

(The toilet in the room a little ways from where I'm sitting has one)