The ornamental design for a supportarm for an overhead surgical lighting system, as shown and described.
FIG. 1 is a perspective view of one end of a support arm for an overhead surgical lighting system, showing my new design;
FIG. 2 is a left side view of the support arm for an overhead surgical lighting system, the right side being a mirror image thereof;
FIG. 3 is an end view thereof;
FIG. 4 is a top view thereof; and,
FIG. 5 is a bottom view thereof.
The broken line showing of support arm for an overhead surgical lighting system is included for the purpose of illustrating unclaimed matter and forms no part of the claimed design.