I also wonder if something like this donut for the mid '90's chevy trucks could work. it has a short length of pipe inside it and is flat on one side.maybe you could find something like this at a local parts store and simply test fit it. if you take the pipe and the original donut with you that part would be simple enough.
https://www.summitracing.com/parts/m...hoCJ8UQAvD_BwE