Can someone help me to find the right replacement filter for the cool mist humidifier V3100?  It says it takes the round one, but it doesn't, it takes the rectangled one. 

I am actually interested in finding out how we can get a small part for our humidifier. We lost the small black rubber seal that fits into the screw on cap. How can we get another so we can keep on using it? Please contact me back at my email. Thank you

I have a few questions.  What is the little round ball in the tank and how do you look after it?  How full can you fill the tank?  If you use the humidifier for a couple of weeks do you have to throw the filter out?  What about using distilled water in the tank?