Amazon.com: Lineco, Natural Waxed Linen Thread 20 Yards, Books by Hand Natural, Black, Brown Color for Sewing, Bookbinding (3/Pkg)
Amazon.com: Books by Hand, Natural Waxed Linen Thread, Three 20 Yard, for Leather Sewing, BBHM206
Amazon.com: Books by Hand Linen Thread, Archival Quality Natural Unbleached and Unwaxed, 50 Yards 35/3 Gauge, Ideal for Bookbinding and Sewing Signatures
How to Choose the Right Bookbinding Thread | Bookbinding Fundamentals