People have gotten the Sony Reader to recharge from a solar charger, but it's a bit fragile for the activities you're talking about, and I don't know how well it would handle sub-freezing temperatures. I know LCD screens can have trouble displaying when it gets cold enough, which probably rules out the eBookwise 1150. That's too bad, because otherwise the eBw is fairly sturdy and the batteries last quite a long time. I'd say the ruggedized PDA yvan suggests is probably the best bet for a very challenging environment, if you can enjoy reading enough on a screen that small.
Otherwise... maybe the OLPC? That has a number of off-grid power options and is meant to be highly durable. You could also use it for many more purposes while you're traveling, like keeping a journal. But it would take up more pack space.