If you do a bit of researching on the net you will see that you can make a
vac chucking system with very little cost. Use an old freezer compressor
for
the vacuum and make a rotating joint with some sealed bearings - the ease
of
the rotating joint manufacture depends on what kind of outboard spindle
arrangement you have.
I used an old 2 piston rather large refrigeration compressor but bought a
Oneway rotating joint. I made my own drum chucks out of ABS pipe
connectors.
Billh

For vacuum, high air-flow is better than high pressure. A household vauum
cleaner is sufficient, provided it has a by-pass valve to stop the vac motor
from burning out from lack of airflow.

Depending on the lathe, a rotation joint is not necessary. A tin can can do
the job! Mine is sized to fit over the handweel and secured to the
headstock with a disk of 1/2" ply, cut in half and drilled to fit closely
around the spindle. Oiling the spindle then applying a bead of silastic
around where the ply joins the spindle seals it enough for the vacuum to
work. (It's highflow, not high-pressure, remember.) A hole cut in the
other tin-can for the hose from the vac and voila!

It generates sufficient pressure to do light touch ups to the foot of a
bowl, careful removal of the tenon, reshaping, etc.

Even a commercial vac-chuck set up won't allow more than a light touchup and
a tin can's a darn sight cheaper...

- Andy