From what Kevin in England and Roy Locke have told me Golde Top parts on Porche's, BMW's, VW's and other cars that have Golde Tops installed on them, also fit our Squarebird Golde Tops. They are usually interchangeable. Here are some companies that you might want to check with.
Sunroof - Golde Top Parts
Read the Golde Top Parts List & Availabilty Thread on this Forum.
This page shows all the Sunroof parts that NLA has available.
In England. You need the VW part numbers to search. You can also email them and describe to them the part that you are looking for. Pictures might help.
Again, photos of parts or broken parts you are looking for might help them find what you need. Call or email these companies and tell that what you are looking for. You might have to tell them you are aware that most Golde Top sunroof parts for their brand of car (Porche, BMW, VW, etc.) also fit the 1960 Squarebird with the Golde Top. Let us know if you have any success with a particular company so we have it as a matter of record for the future.