Your "connect to the world" limitation rules out just using your phone (which is really the most straightforward answer).

But is there some reason you can't just pickup a second-hand unlocked Android phone, no-sim, preferably with a user-replaceable battery, and then load it with a pod-cast listening app. such as:

https://f-droid.org/en/packages/de.ph1b.audiobook/

If you turn off all the radios (airplane mode) and don't run the screen that often, you might also come close to your day-or-two without recharge requirement as well.