As the z39.50 client in NGL doesn't work for me, they recommended using MarcEdit's z39.50/SRU client. They already have Library of Congress' server setup builtin, and you can add your favorites as well. Just click "retrieve unicode" so the record you'll download is Unicode-compatible:
After you search, you can download the result in a .mrc file which can be opened with notepad or your favorite text editor. Copy all of the text of the file and then in the cataloging module, select "paste MARC record from clip board" in the cataloging module.
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