and you could use a 120 to 30 volt transformer and simply apply 120 to the 30 volt side

210.6 Branch-Circuit Voltage Limitations. The nominal
voltage of branch circuits shall not exceed the values permitted
by 210.6(A) through (E).

(A) Occupancy Limitation. In dwelling units and guest
rooms or guest suites of hotels, motels, and similar occupancies,
the voltage shall not exceed 120 volts, nominal, between
conductors that supply the terminals of the following:

(1) Luminaires

(2) Cord-and-plug-connected loads 1440 volt-amperes,
nominal, or less or less than 1⁄4 hp

Any pics of the fixture? Most fixtures will take retrofit ballast mounts well.

If this is permanent, I would just change the ballast. Technically speaking, lighting over 120 volts is not allowed in residential settings in the US. From the 2014 NEC