Many of the 20th century revival instruments - de Blaise, Sperrhake immediately coming to mind were built with leather plectra. Not to be confused with the duller peau de beouf, these sharply cut stiff leather plectra were long lasting but eventually after decades become brittle and need replacing.
The normal approach is to drill a slot at the top of the leather and insert delrin plectra, most people not having experience of leather. But to my delight the other day I discovered Durand in Surrey - http://www.musicroomworkshop.co.uk
who trained with Dolmetsch and therefore are experienced in replacing leather plectra . . .
So harpsichords with leather quilling can now sing again!