Where can I get the Android 4.2 rom for Acer B1-730HD to downgrade it?

[AC Question]

Android 4.2 rom for Acer B1-730HD

Hi.
I need to downgrade an Acer B1-730HD from 4.4.2 to 4.2 but have been unable to find any official rom.

Does anyone know if this is available anywhere please?

Thanks.