Not surprised exactly, where most parts seem available this is probably something that tends to get junked in favor of pods.Surprised you haven't had a ton of offers?
There are two types and I don't remember which is which.
Get a picture of the one you have and closer picture of whats missing.
I have both types here, one bike only had 860 miles when I got it in 2004.
Do you also need the extra long stud that goes through both boxes?