I have small square shaped vent in my bathroom. But it is very weak in terms ventilating the air and mold is starting to form on the ceiling. I was wondering if anyone has any suggestions for a small exhaust fan that i can attach to the vent. My requirements are the following. It is easily attachable. I have no problem having to glue it on. It has to be battery powered. It would no be possible for it to be powered by an electrical cord. Thank you!