I am looking for something that I am not too sure I will find.
In my last house, the previous owner had a device for cleaning his chimney. It was for a square chimney and was adjustable.
The device was about 14" long, and 6" x 6" when collapsed. When open, it would expand to about 14" x 14".
It was designed such that you would go to the roof, lower the device down the chimney until it hit the bottom, then pull on the rope very hard and the device would expand and you pull it up the chimney. repeat about 2-3 times, then go and shovel out the creosote/debris. I would do this about every 2 months during the heating season.
When I sold the house, I did not keep that device since I would living in an apartment and had no use for it. Now that I have a square chimney again, it would be nice to have.