[Amps] looking for source of air flow switch

[Fern Rivard]

    I'm in the process of putting together a hb hf amp using the Eimac 8877 tube. I want to make sure that it's bullet proof in case I should have a failure with the blower so I'm trying to find a source of air flow switch similar to what I believe some Henry amps used  a Rotron 2A-1000 but I can't find anything on that switch anywheres. Any leads would be much appreciated.
    Thanks from Fern