While it isn't quite what you wanted, you can do this with a common event!
You won't be using the actual game over screen, but rather pictures.
This way may be more customizable than a plugin as well... you can define what the conditions are for death (such as not having a certain item in your inventory, all players reaching 0 health, one player reaching 0 health, etc.)
You can also give the players an option at the end to load their game or go back to the title screen

You could just do a wait command and force them to go back to the title screen, too.
Here's how you do it, if you are pretty competent with events it should be easy enough to customize. You can just use this until someone comes along with the exact plugin you need. It's definitely a workaround, but could also be a solution.
If you have any questions, let me know!
Note, I'm not sure if this will work during a battle or not. You may have to set up some conditions in each troop to make it look like this common event page. Like I said, workaround, for now.