Sounds like maybe the Onyx Boox 60/BeBook Neo might be worth taking a look at. It's a bit more than your $300, but does seem to have most/all of your desired features. I don't own one, but HarryT one of our Mods who has a bunch of readers says it's his favorite.
I'm sure there are other sellers in the US, but here's a link to Dulin's. He's also a forum member so you should be able to PM him with questions if need be...
http://www.dulinsbooks.com/index.php...d=655&parent=0