Hi Robert,
I tried Draeger first of all and they no longer support this warmer and have no spares for it. I then tried RAFI and Ledex who made the switch and they say it is now obsolete and can't think of another switch we could use instead.
I was hoping that maybe someone might have one tucked away in their stores somewhere.
If I can't find anything suitable I expect this poor old beast may have to be retired!