The National Association of Watch and Clock Collectors (NAWCC) promotes horology.  This weekend, they are having a sale on extra books from their library as well as tools and parts:

Up to 25% off sale on selected items in NAWCC’s eBay store.

Be sure to check it out.  If you are not already a member, please consider joining  (you can say, C. Hooper #102101 referred you).