Spare Hardware Parts Billy Shelf Pins (Compatible with IKEA Part #131372) (Pack of 12) : Amazon.co.uk: DIY & Tools
101532 IKEA BILLY SHELF SUPPORTS PINS FIXINGS PEGS METOD UTRUSTA original spares | eBay
131295 IKEA Fjalkinge Cabinet Shelf Pins Bracket Steel Support Part IKEA for sale online | eBay
IKEA BILLY SHELF SUPPORTS PINS PEGS FIXINGS All 3 styles in stock GENUINE PARTS | eBay
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.
IKEA BILLY Shelf Pins #101532 – FurnitureParts.com