I've only read the first page of the other thread.
https://www.google.com/search?q=+Eberspacher+evtv
EVTV like the ceramic heater in the Chevy Volt; I think it heats water and not air. The link points to blog posts and videos about controlling it with an Ardiuno.
OEM parts available in your nearest junkyard. I forget what they pay, maybe one-fiddy.