Simple cardboard box with holes poked in it.
String ribbon or fabric between two holes.
(yarn tends to break quickly)
Repeat till all holes are connected.
Attach beads to both ends for easy grabbing and
to stop the ribbon or fabric from disappearing inside the box.
Add some weight inside the box. I used more beads,
they make a nice sound when the box moves.
Seal it shut.
Wait for children to discover what happens when they pull on a bead.