IKEA BILLY Shelf Pins #121762 – FurnitureParts.com
RAMSHULT Bracket, white, 7x8 ¾" - IKEA
IKEA Billy bookcase tip: if you have an OLD Billy bookcase (pre-2014) you can still add extra shelves even though the new extra shelves from IKEA use a new, disc-shaped shelf pin.
NEW Shelf Brackets for IKEA DETOLF Add 3 Extra Shelves - Etsy
Amazon.com: Spare Hardware Parts Billy Bookshelf Pins (Replacement for IKEA Part #131372) (Pack of 8) : Home & Kitchen
Amazon.com: ReplacementScrews White Shelf Support Pins Compatible with IKEA Part 101558 (Pax, KOMPLEMENT) (Pack of 8) : Home & Kitchen