4 model

Free

(BILLY) Bookcase Spoolholder

Thingiverse

Free

Hook Shelf Mount for Billy Bookcase (Adjustable)

Thingiverse

Free

Manga Riser - Billy Bookcase, Omnibus Height

Thingiverse

Free

Mini Bookshelf - Ikea Billy Bookcase inspired (no supports needed)

Thingiverse