The Onyx Boox i62HD I have has turn buttons on the sides. I find them very confortable to hold it with one hand. Pressing the right button on the upper side goes to the following page, and on the lower side goes to the previous page. The left button works the opposite way: the upper side goes to the previous page and the lower side to the following one. This way you can easily go to the previous or the following page using only one hand.
You have more info here: http://ereader-store.de/en/onyx-boox...oft-touch.html
There is a lighted version too (Firefly).
The only thing I do not know if you're going to like is the weight: 250 gr. It doesn't bother me, but I don't know how much the 505 weights