DOCUMENT Records (UK) has issued almost every Leadbelly recording,
including the Library of Congress material.
Better sound, annotations, packaging on the CD's issued by the owning companies (e.g. Smithsonian-Folkways, Columbia, RCA), usually. However, Document's complete chronological presentation is worth having, and has material not otherwise available.

Document Records LEADBELLY

http://www.document-records.com/results.asp?Submit=Go&select=Leadbelly&offset=10

Best wishes, Thomas.