I have a Samsung Convoy II. It's not super-thin, but it does pretty well as just a phone (plus texts). It actually has a decent web browser for when you need to check email (about once a month something comes up). Ruggedized, waterproof, and well-made. I think I paid $70 for it on eBay (in brand-new condition). Doesn't have an e-ink display, but I'll deal with that.

I got a low-battery warning this morning, and realized that I hadn't charged it since last Sunday (a week ago). Plugged it in for an hour, and the battery was full again.