I just read this article and one of the people from MPI is supposed to be working with manufacturers overseas to make new heaters and parts to service the old ones. Hopefully they will produce the burner rings and whatnot.
hxxp://www.pressherald.com/2015/09/28/when-temperatures-fall-mainers-call-in-the-monitor-man/
hxxp://www.pressherald.com/2015/09/28/when-temperatures-fall-mainers-call-in-the-monitor-man/