Hi,
Don't know the machine but was wondering if the on/off switch is Item #44 - part number [https://www.partssource.com/parts/draeger-inc/4109768|4109768] (possible supplier?) as seen on p.8-5 of the [http://www.wemed1.com/downloads/dl/file/id/7951/product/4617/service_manual_for_an_nad_nark2b.pdf|service manual].
If not maybe you could contact the supplier shown in the link and ask them,
Hopefully this is of some help.