The ornamental design for a touch up paintpen, as shown and described.
FIG. 1 is a front and top perspective view of a touch up paint pen, showing my new design;
FIG. 2 is a rear and bottom perspective view thereof;
FIG. 3 is a front elevation view thereof;
FIG. 4 is a rear elevation view thereof;
FIG. 5 is a left side elevation view thereof;
FIG. 6 is a right side elevation view thereof;
FIG. 7 is a top plan view thereof;
FIG. 8 is a bottom plan view thereof;
FIG. 9 is a perspective view thereof, shown in an alternative position;
FIG. 10 is another perspective view thereof, shown in an alternative position; and,
FIG. 11 is an enlarged view of a portion indicated with numeric 11 in FIG. 2.
The broken lines in the figures illustrate portions of the touch up paint pen that form no part of the claimed design. The dash dot dash lines in FIGS. 2 and 11 are for the purpose of depicting the boundary lines of the enlarged view and form no part of the claimed design.