Wire size for Yamaha M1J

[Maxpiano]

List -

I have just received a request from a missionary in Sudan, for a piece of
music wire to replace a string on a Yamaha M1J.  B4 is the note.

I don't have this model among the pianos I service, so I don't have a source
to check.  I would assume that the corresponding size for an M2XX or M3A would
do in a pinch.

Any help appreciated

Bill Maxim, Simpsonville, SC