> In a pinch you can use heavy duty cotton thread, but the best
> material is the woven type of cord that is used in the tuning dial
> apparatus of older radios.

That's called "dial cord" and I believe it still can be obtained from
Antique Electronic Supply in Arizona.  Another thing I sometimes used
when re-stringing radio dials was fishing line which looks almost the
same as dial cord.

Hal Davis