I'm just asking because I found this in my latest game and I believe it's an error. It's not listed in Dredmorpedia, so it's not from any of the mods that are listed there (Roguish Renovation, etc.).
Have you tried FaxPax? It's what people check first when something from hell-if-they-know-where breaks in some insane way.
I already checked that -- FaxPax adds a similar but different item -- it has different graphics and a different name ("Dashing Top Hat", plus it's a head item, not torso item). BTW, the name of the item is "Tophat" not "Top Hat" -- sorry about that (just loaded up my save game to verify).