Bacharach Instrument makes a nice liquid manometer.  Since it uses a
highly viscous fluid with a high specific gravity, the Bacharach
instrument is only about half as long as a comparable water manometer,
and the viscosity of the fluid dampens its motion, making quick
measurements easier.  The only problem is that mine only measures up to
20" w.c.  I would suspect that Bacharach may make a larger model for
higher pressure use (mine was designed primarily for combustion
testing).

Dwyer makes a roll-up water manometer kit in several sizes, reading up
to 60" w.c.  The sheer length of a water manometer reading this high of
pressure makes it unwieldy to use, however.

Dwyer also makes a reasonably good mechanical gauge in their
"Magnehelic" series.  These may be had in various ranges up to
100" w.c.

For higher accuracy, try an "pressure instrument test gauge."  Although
expensive, they have accuracies of about plus or minus 0.25%.  Also,
most are calibrated in inches of mercury, which will require making up
a conversion table for use with the gauge.

With the exception of the Bacharach manometer, all of the gauges above
are available nationwide from W. W. Grainger (wwgrainger.com).  Although
Grainger's sells Bacharach instruments, they don't list Bacharach
manometers separate from their "Fyrite" combustion test kits.  Perhaps
they could special-order one for you.  Alternatively, one could try
getting one from a heating and cooling supply house, an engineering
supply firm or a combustion controls supplier.  When buying from
Grainger's, it has to be done on a company name (they're a "wholesale"
supply house, even though their catalog prices are "retail").

Good luck.

Dave Vincent