72 Washer bottle neck extension

[Mooser]

So I understand that they do not repro the proper next extension for a 72' w/o air. The GM replacement of the newer style is not even close to fitting.
Does anyone have a proper extension that actually fits?
I'd like a picture of one so I have some idea what to keep my eyes open for, a part number off of the actual neck would be great too.
Thanks
Mooser