If you go eink you need a big device with a 9,7" screen, as there are Onyx M91/92, Pocketbook 902 or Kindle DXG. But as you've already mentioned it can take some time to turn pages. You must find a balance between fast page turning (and live with a ghosting effect) or slower page turning (and no ghosting effect).
It might be an idea to investigate into convertible laptops like this one:
http://www.amazon.de/Fujitsu-Lifeboo...466550&sr=1-81
I'm afraid this will be out of your financial budget, but maybe you have the possibility to get a used one at a reasonable price. They are very useful for students.