Heck, you didn't include the bit that states "2-5 days". Up to 5 days, really?! I can fashion myself a pot from clay, fire it, then use the same fire to boil the water in that amount of time. Now, if you were out for weeks at a time, with spares that you could swap into the Steripen, and into the charger, that would work ok.In the blurb for that Steripen charger, note that it says it takes 2 days to recharge 2 cells!
I got a Shekor charger due to its voltage input range :
All I need now is the solar panel ..
Several chargers will work from 12v ...
So get a car battery , hook up a solar cell to charge the car battery and use the car battery to power your charger ...
Or buy a Shekor , and hook it up directly to a solar cell / panel ..
Thats the plan in anyway ...