Do you know how to take it apart? Unscrew the screen/plunger assembly? Once you do that, I'd use baking soda (greatest cheap stuff on earth), and, as other's said here, a tooth brush or pot scrubbing brush and make a paste. . . that should remove the mold. . for fun, you could add some ww vinegar to your baking soda paste for a blast of foaming . . . stuff. . rinse well.
Good idea to do that about once a month anyway. The BS will neutralize the acids left in any residual coffee. . . .