The ornamental design for a portable caneholder, as shown and described.
FIG. 1 is a front perspective view of a portable cane holder, showing my new design;
FIG. 2 is a front elevation view thereof;
FIG. 3 is a rear elevation view thereof;
FIG. 4 is a left side elevation view thereof;
FIG. 5 is a right side elevation view thereof;
FIG. 6 is a top view thereof;
FIG. 7 is a bottom view thereof; and,
FIG. 8 is a perspective view thereof in its intended environment of use.
The broken line showings of FIG. 8 of a shopping cart and a cane are for the purpose of illustrating environmental structure and form no part of the claimed design.