If changing pulleys does not get the job done, you can get a small
inverter or UPS [uninterruptable power supply] of adequate capacity for
the desired frequency, and substitute a 12- or 24-volt DC power supply
for the battery (sized as required).  The inverter will probably be
cheaper, as it does not include a battery charger.

There can be a couple of issues.  Many of them have a "modified sine
wave" output, which might make an inductive load like a motor "sing" or
buzz from the harmonics, and really cheap units put out nearly a square
wave [lots of harmonics].  Most inductive loads won't absorb power at
harmonics of the base frequency, which can lead to excessively high
voltages at these harmonics, causing the UPS or inverter to blow out
its switching devices.

I bought a 3-kilowatt Xantrex inverter for a hundred bucks which can
run many of the loads in our fifth wheel camper.  It does make the
ceiling fans buzz, but it has no problems starting them.  However, it
won't start a SkilSaw.  I've seen them on eBay in both 50 and 60 Hz
versions.

Steve McCollum