Glenn has a 26 year old prefabricated chimney and the top section is rusted out. He can't find anyone who has a replacement section for the chimney. So he asked if I could find it, and if not, whether he could screw something else to the top of his chimney.
It turns out that his particular chimney company was bought out by another one in 1994 and his model of chimney is no longer manufactured, and there is no more stock. Apparently nothing else will fit the twist-on socketed arrangement of his particular chimney. Bad news.
Can you screw something else on? Not really. The problem is that these chimneys are actually sealed all around with insulation on the inside. If you start putting screw holes through the jacket, you will be letting water in, which will cause serious problems with the insulation, and hence the performance and durability of the chimney. Unfortunately it is time to change the chimney. Maybe I could talk Glenn into installing it "inside the house" this time -- the new one would work better than the old one because you would be eliminating the cold downdraft that fights the start-up fire.