After reading the request for a source for a turbine suction box,
I thought of another possibility.  In the good old days when printing
was done with plates made from negatives, large "copy cameras" were
used to make the negatives from paper copy.  Vacuum pumps were used
in these cameras to hold the negatives flat against the camera back.

These cameras, once expensive, are now junk and show up in any large
recycling center or at the dump along with their suction boxes.  I got
one for about $20 recently that is a well-made unit with a heavy steel
enclosure and felt noise baffling.  The motors are of the correct type
-- with cooling air independent of the vacuum connection as they were
intended to be operated with the intake fully blocked without burning
up.

I'm sure there are hundreds or thousands of these things lurking in
used equipment warehouses unless they have all been dumped by now.
When operated a reduced speed and/or with additional baffling, they
could make a suitable piano pump although this is a pretty bad idea
in most cases as few pianos really should be powered this way.

Best regards,
Spencer Chase