Where can I find a used or new Apple Watch with iOS 9 installed

I have an iPhone 8 Plus with max memory I purchased brand new. Not Cheap! Along with a iwatch 3 that worked perfectly with it. I moved up to the series 7 after my heart attack. Loved the watch then my watch band broke two weeks ago and it hit a concrete floor back side down and the Sensors broke. I depend on this watch to detect Afib and do AKG’s. It has saved my life twice. I’m now retired and live on a fixed income so a new phone is out of the question plus where I live there is no 5G anywhere the other other reason to buy a new phone. I thought this would be a simple process. Buy another Iwatch 7 so I have ( Twice now ) and have to return it again. Imagine my surprise when I found out it could no longer pair with my iPhone 8 Plus. Why ? Because they have iOS 10 installed in the watch which makes it’s no longer compatible.

I am trying desperately to find either a series 6 or 7 iwatch with iOS 9 installed. Originally Apple did something truly amazing and special when they added heart detection and EKG to the watches. Why would they purposely take ability away from existing users unless it’s just to force us to upgrade. I have always been a stanch supporter of apple until now. Currently I own 2 Apple computers, a tablet. My wife and I both have apple 8 phones and iwatches. It sad and sucks that apparently they just don’t care anymore. Please help me find another one with iOS 9 still in it