FWIW ...
I had that same made in China humidifier in a new/old humidor I bought. Neither one appeared to ever have been used. But before I did anything with that setup, I drilled a small hole in the back of the plastic humidifier and used a dental tool to pry the bottom section away from the top/sides, being careful not to crack the plastic. Threw out the foam, filled it with Cigar Mechanic beads, and sparingly used some super glue to seal it back together. Let it air a few days in case the super glue carried any fumes, and voila -- back in business, new and improved.
Although, I could see not wanting to use a humidifier that has had a mold issue in the past...