I claim the ornamental design for an arch cap for enclosure for a recreational structure, as shown and described.
FIG. 1 is a perspective side view showing four arch caps for an enclosure for a recreational structure according to the subject matter disclosed herein;
FIG. 2 is an overhead perspective view of one arch cap for an enclosure for a recreational structure according to the subject matter disclosed herein; and,
FIG. 3 is a top view of the four arch caps of FIG. 1 for an enclosure for a recreational structure according to the subject matter disclosed herein.
The broken line showing is included for the purpose of illustrating and forms no part of the claimed design.