FIG. 1 is a perspective view of the notepad attachment to a cupholder showing a new ornamental design therefor;

FIG. 2 is a right side elevation view thereof;

FIG. 3 is a left side elevation view thereof;

FIG. 4 is a rear elevation view thereof;

FIG. 5 is a front elevation view thereof;

FIG. 6 is a top plan view thereof; and,

FIG. 7 is a bottom plan view thereof.

The subject matter indicated by dashed lines in the drawings is shown for reference only and does not comprise part of the claimed design. The pen and notepad of FIG. 1 are shown for reference only and do not comprise part of the claimed design.