I realise that I don't know the full range of considerations you will be taking into account, particularly the quantities involved which will make a big difference to the options open to you. But conveniently ignoring all that here's my take.
What's the expected life of this product/the vehicle it's installed in? If it's more than three years then an off-the-shelf Li-ion powered tablet may not be the ideal device to use.
Perhaps an industrial Android tablet - more expensive but probably a whole lot better built and better sealed. A decent supplier of such things should be able to have a rational discussion with you about your concerns and requirements.
If it is permanently installed in the vehicle something running off the vehicle's electrical system would be optimal. For a limited number of devices perhaps a commercial tablet with the battery stripped out. See industrial tablet supplier above. Most tablets will run when when connected to a charger with no battery present or you simulate charging the missing battery with a 3.7V Zener in series with a resistor (Afterthought : put a supercapacitor across the Zener and if the Zener won't take the forward current if the supply fails put a normal diode in series with the Zener. Experimentation needed
) . For greater device numbers perhaps a custom device from an industrial supplier, or maybe there is one out there waiting to be discovered.
In the extremis your own engineering solution using bought-in components and displays packed appropriately.
