Armrest for working machine

FIG. 1 is a perspective view of an armrest for working machine showing our new design;

FIG. 2 is a front view thereof;

FIG. 3 is a back view thereof;

FIG. 4 is a top view thereof;

FIG. 5 is a bottom view thereof;

FIG. 6 is a right side view thereof; and,

FIG. 7 is a left side view thereof.

The broken lines in the drawing views are included to show unclaimed subject matter only and form no part of the claimed design.