There is no membership roster. A lot of members wanted to remain anonymous and a lot of membership lists were destroyed when the US joined WWII.

The FBI files on the Bund are online here:

https://vault.fbi.gov/german-american-bund

There are lists of members and leaders in the files but it's not complete or accurate. For example, law enforcement just recorded plates of vehicles at bund camps or rallies but could have recorded reporters visiting the camps or non members who were visiting because of curiosity or friends.

What exactly are you looking for, maybe I can help. I'm writing a book on the bund and did my Master's thesis on them.