The ornamental design for a refillcontainer for marker, as shown and described.
FIG. 1 is a perspective view of a refill container for marker;
FIG. 2 is a front view thereof;
FIG. 3 is a rear view thereof;
FIG. 4 is a left side view thereof;
FIG. 5 is a right side view thereof;
FIG. 6 is a top view thereof;
FIG. 7 is a bottom view thereof; and,
FIG. 8 is a side view showing the refill container in use wherein the cap is removed.
The broken lines showing the bottom in FIG. 7 and the liquid and marker in FIG. 8 are included to show features on the refill container and in the environment that form no part of the claimed design.