I would start my Shure support. It may take a few tries, but they have a couple of women who use to work in support that knew every part for those older (discontiuned) microphones.http://www.shure.com/
The Data Sheets on Shure's web iste list a 7A, but not a 7B model:http://www.shure.com/datasheets/guides-discontinued.html
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