Amazon.com: FurnitureParts.com IKEA Billy Shelf Pins #131372 (12 Pack) : Tools & Home Improvement
IKEA Shelf Support Pins Part # 114258 (8 Pack) Furniture Hardware Part – Discouch
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.
3DP Additional shelf supports for showcase DETOLF - IKEA by NationalRacers3D