@jessed First, I am not a vest user, but one was offered some years ago and I declined.
Here is what my current pulmonologist uses as her criteria for "which vest" -
1) a trial period during which it can be returned without penalty - preferably 90 days, but at least 30.
2) in person support to set up, adjust & teach.
3) not for those with osteoporosis or serious arthritis in spine or rib cage.
I will add, based on years of reading on Connect - multiple sizes. There is a HUGE difference in size between someone 5 feet tall and 110 pounds and someone 5'7"and 150 pounds.
Your pulmonologist may only be offering what is supported locally. Did you ask?