Amazon is reportedly planning to release a solar-powered case for the Kindle Oasis, but thanks to one industrious hacker it's going to be the second premium ereader with a solar case, rather than the first.
A Kobo Aura H20 owner has crafted a one of a kind case for their ereader. They combined a cheap after market case with a couple solar panels and a USB cable to create a case which can charge their ereader on the go.
The hacker cut out sections of the inner liner to fit the panels, wired them to the USB cable, and glued them in place.
The resulting DIY solar-case can't match the output of a standard wall charger, but the hacker did report that the panels provided enough power, both in direct sunlight and inside a building, to trickle charge the Aura H2O.
They haven't posted a complete set of instructions, but the photos I found over at MobileRead look straightforward enough.
It shouldn't be too hard to duplicate this project if you have the necessary skills.
I don't, so if I were in need of a solar charger I would get one off of Amazon or Ebay. You can find all sorts of chargers there, including ones with a USB cable, and best of all those commercial kits are both cheaper than the home-made charger shown above as well as more useful (they're capable of charging items other than just an ereader).
That's why I have never been tempted to copy the solar-powered ereader mods I've seen over the years.