tried some 20lb. fly line backing for bobber stops. it measures .020 dia.
works perfect!
i keep it on spool. i cut a short piece off, and just tie it on the fishing line with a uni-knot.
short grub LIKED above post
A lot of folks swear by the Lindy string stops. They hold well due to the fact that the string is cotton. Find some cotton string and make your own for a fraction of the cost of store bought.