Please ignore my image request above; I was able to revive my reader with the following steps.
Maybe these steps will help someone.
Please let me know in which topic I should post this:
I got lucky because my reader's 4GB internal card definitely got corrupted, but apparently only for writing. It became read-only.
I was able to create an SD card image from it and imaged a new 8GB card.
The device booted successfully and all my settings and mods were preserved.
Then I removed the card again and extended the KOBOeReader partition to take up the rest of empty space on the card.
Booted the device again and voila!
Hopefully this will save someone the extra pain.
The software I used:
To read my "corrupted" SD card into an image:
Flash Drive Image Creator (available at
https://www.vconsole.com/download)
To write the SD Card image onto the new card:
Flash Drive Image Writer (available at
https://www.vconsole.com/download)
Resizing the partition:
MiniTool Partition Wizard Free 12.1 (Available at
https://www.partitionwizard.com/free...n-manager.html)
Important!
The Antivirus and AntiRansomware software interfered with SD Card writing process therefore I had to disable them temporarily.