I had a McKee and learned that John Deere marketed the McKee blower just painted it green. They also made smaller blowers for Kubota in Canada
I got many parts for my McKee 720 from a local John Deere dealer.
Here is a link to a chain idler sprocket which leads me to believe that Ackland Grainiger carry a variety of them. https://www.acklandsgrainger.com/AG...y.do?gclid=CKmxxef-08cCFZSCaQodXz8NiQ&item_co