FIG. 1 is a perspective view of a keyed emergency stop cover, showing my new design; FIG. 2 is a front view of the design of FIG. 1; FIG. 3 is a rear view of the design of FIG. 1; FIG. 4 is a left side elevational view of the design of FIG. 1; FIG. 5 is a right side elevational view of the design of FIG. 1; and, FIG. 6 is a top plan view of the design of FIG. 1.