What about a 2-1 step down transformer? That could do it without putting current through the safety ground.

An adequate step down transformer will certainly work, but it will consume power constantly unless it is wired in past the 120 volt device switch. AND it needs to be mounted someplace. And a reliable transformer will cost more than the added extra white neutral wire.

 

And a reliable transformer will cost more than the added extra white neutral wire.

Not if the wiring is in the walls! Which is almost a certainty.

 

In a multi-unit dwelling that would probably be the case.. But in most single family dwellings in my area there is access from either below or above.
AND one additional thought is that the need is only for a lower current neutral connection, any nearby electrical junction box, such as outlet or switch, would probably afford an adequate neutral connection. The exception being circuits with a GFCI device in the breaker panel. I regard that as a rather dumb place for a GFCI device serving multiple locations.