Hi Joe,

You could contact some stores that cater to land surveyors. There are
some three-phase 115V 400Hz gyros used in that field, or at least they
used to. Since they often work off grid using a 12V battery there should
be inverters offered. I have seen one a long time ago and since these
gyros use so much power the inverter is kind of large, it was the size
of a brick.

Regards, Joerg

http://www.analogconsultants.com