The ornamental design for an interchangeablecover for a stanchion, as shown and described.
FIG. 1 is a perspective view of an interchangeable cover for a stanchion.
FIG. 2 is a perspective view of the cover.
FIG. 3 is a left view of the cover.
FIG. 4 is a right view of the cover, the front and back view are symmetric.
FIG. 5 is a top view of the cover; and,
FIG. 6 is a bottom view of the cover.
The broken lines shown in FIG. 1 illustrate environment and forms no part of the claimed design. The additional broken lines shown in FIGS. 1-5 illustrate portions of the interchangeable cover for a stanchion that form no part of the design.