The ornamental design for a portablelamp, as shown and described.
FIG. 1 is a perspective view of the portable lamp;
FIG. 2 is a side view, which is identical for all sides including front and back, of the portable lamp;
FIG. 3 is a top view of the portable lamp; and,
FIG. 4 is a bottom view of the portable lamp.
The broken lines showing of the cord element in FIG. 1 is for environmental purposes only. All other broken lines show portions of the article not claimed. The broken lines form no part of the claimed design.