Nylon Mesh Tube
Rather fascinating stuff. We've swiped this stuff from the hardware store - electrical department - where it was designed to contain electrical wires. (Which some folks do actually use it for. Especially airplane builders. ;-) )
It is very resilient, you can squash it down to get it through a bead, and then it will spring back.
To get it through a bead, squash down the end and wrap with tape, and thread through your beads, then cut the taped part off.