http://www.worthingtonagparts.com/John-Deere-Auger-Clean-Grain-Connection-Solid-USED-WU-H78850 Probably should call these places they are calling it a hoop? Best way to find leads on stuff is type in the actual part number in a search engine and see what turns up. It's how I came across the inner hood liners.
https://www.greenfarmparts.com/John-Deere-Hoop-H78850-p/h78850.htm http://www.plainsequipmentgroup.com/buy-parts/John-Deere-Part-H78850-HOOP-1889284/ | 
clean grain auger tube 4400 jd combine
