Something similar in design to your Libra 2 would be the Pocketbook Era which comes in 16 and 64 gb and has a color version. I can't say if it's speedier and more responsive than your Libra as I've used neither but it is 7in, waterproof(ipx8), has adjustable front light, has buttons(on the edge of the device though), and you can use KOreader on it too.
This thread has discussion on other perks to Pocketbook.