FIG. 1 illustrates a perspective view of the claimed design for a loop chest slide attachment; FIG. 2 illustrates a front view thereof; FIG. 3 illustrates a rear view thereof; FIG. 4 illustrates a top view thereof; FIG. 5 illustrates a bottom view thereof; FIG. 6 illustrates a left-side view thereof; and, FIG. 7 illustrates a right-side view thereof.