Amended to add Blackstone & Books on Tape also offer replacement discs.
MicroMarketing is a favorite, 4 votes with a couple of
libraries having used their services before. Advantages: offer
replacement discs, use replaceable sleeves & containers, can be
ordered with cataloguing & labels.
Midwest Tapes - 3 Also can ship with barcodes & labels. Complicated website.
Blackstone - 4 Library editions last slightly longer. Also offer replacement discs. Primary distributor for Recorded Books now.
Brilliance Audio - 2 Damage easily, can't repair by buffing.
Books on Tape - 1 Also offer replacement discs
Ingram - 1
Recorded Books - expensive, but durable ($65-110 each)