FIG. 1 is a front, top, and right side perspective view of a fragrance diffuser cartridge showing my new design;

FIG. 2 is a top plan view thereof;

FIG. 3 is a front elevation view thereof;

FIG. 4 is a right side elevation view thereof, the opposite side being a mirror image of that shown;

FIG. 5 is a bottom plan view thereof; and,

FIG. 6 is a rear elevation plan view thereof.

The ornamental design which is claimed is shown in solid lines in the drawings. The broken lines in the drawings are for illustrative purposes only and form no part of the claimed design.