We claim the ornamental design for a detachable unit for portable computer, as shown and described.
FIG. 1 is a front perspective view of a detachable unit for portable computer of the present invention;
FIG. 2 is a front view thereof;
FIG. 3 is a rear view thereof;
FIG. 4 is a first side view thereof;
FIG. 5 is a second side view thereof;
FIG. 6 is a top view thereof;
FIG. 7 is a bottom view thereof; and,
FIG. 8 is a front perspective view thereof shown in an environmental use thereof.
The broken lines shown represent unclaimed subject matter and form no part of the claimed design. Additionally, the unevenly broken lines in the drawings define the limits of the claimed design.