NuVision Android tablet stuck in boot loop

I have:

• My mom's NuVision TM800A510L (similar to Acer Iconia A1-840) stuck in boot loop.


• I can get it into fastboot mode, and recovery mode waiting for ADB sideload.


• ADB and fastboot recognize the connected device, but commands are ignored by the tablet.


• I'm a novice, having once stumbled through a cyanogenmod flash.


• Working from a chromebook running Ubuntu, with Android SDK seemingly properly installed.

Goal:
To restore the factory OS, vanilla Android, or an alternate ROM. Anything to get it running.

I've tried:
Wiping cache, factory reset.
Can't find factory or custom rom anywhere. Customer service refused to provide it.
Following tutorials to bake a custom rom. They all seem to require a system for the tablet to start from.
Pulling partitions from tablet (failed command)
Pushing / flashing / SD boot of ROM for the Acer version of the tablet (format not recognized)

Does anyone happen to have the update.zip for this Nuvision device I can simply sideload? Or anything else I can try?