The ornamental design for a button and spout assembly, as shown and described.
FIG. 1 is a top plan view of a button and spout assembly showing our new design;
FIG. 2 is a front plan view thereof;
FIG. 3 is a left side view thereof;
FIG. 4 is a right side view thereof;
FIG. 5 is a rear view thereof; and,
FIG. 6 is a front perspective view of our new design.
The broken lines showing the nut and washer are included for the purpose of illustrating a portion of the button and spout assembly that forms no part of the claimed design.