The ornamental design for a portable wineglassholder, as shown and described.
FIG. 1 is a front perspective view of the portable wine glass holder.
FIG. 2 is a front perspective view of the portable wine glass holder retaining a wine glass.
FIG. 3 is a top view of the portable wine glass holder.
FIG. 4 is a bottom view of the portable wine glass holder.
FIG. 5 is a right elevation view of the portable wine glass holder
FIG. 6 is a left elevation view of the portable wine glass holder
FIG. 7 is a front elevation view of the portable wine glass holder; and,
FIG. 8 is a rear elevation view of the portable wine glass holder.
The broken lines in the drawings depict portions that are not part of the claimed design, but rather show the environment in which the design is associated.