[Pajamaman]

Onyx Boox are similar to Likebooks. Most people consider Boox to be slightly superior to Likebook, but Likebook are a little cheaper. I'm not sure what size you want. Onyx do a 6" Poke which will be closer to $200. Both Onyx and Likebook do a 7.8" model. These Chinese models are locked down and hard to impossible to root, but have heaps of built-in functionality. They both probably dial home to some Chinese corporation. They are very good devices. Pretty sure you can connect to Onyx via adb, but have to jump through loops. These chinese Android devices are odd beasts, but very good too.

Alternatively, you could get a Kobo. You have to register it, but just use a fake email, then turn off wifi. It is possible to install a note taker, but it will be primitive compared to an Android device. Kobos come rooted out of the box. They are Linux, not Android. You can install Koreader for pdf.

Nooks are much cheaper and can be rooted. They are Android. have to register it, but just use a fake email, then turn off wifi. You can get one in your price point from ebay, 6" or 7.8". Really nice screen. You can root it and install nookmananger, then install an android note taking app, etc. They are far less powerful than an Onyx/Likebook, but much cheaper, and the screen is great. You can install Koreader to read pdf. You can definately connect it via adb.