I got mine when I explained to my pulmonologist I was having a hard time coughing up some of the thick phlegm. He gave me a device right there in the office. No charge. It is an "AerobikA". I mostly use it when I am having a hard time coughing up some phlegm that is stuck in an airway. [You know we all have had them, knowing it needs to come out and even makes a whistling sound when you breathe.] It is hard to get enough air behind it to do the huffing cough and get them out.
Well the doctor explained doing 4 or8 breaths though the device will help loosen the phlegm up and allow me to clear it out.
You can also hook it up to your nebulizer but thus far I use it all by it self.

So next visit just ask the doctor for it or call his office I bet he could have one sent out.
I have also heard you can buy them on Amazon.