When I did mine I got the zephyr from  the Leather Supply House,
http://www.leathersupplyhouse.com/  Seems to be very nice material,
with none of the issues others have reported with zephyr.

Before re-doing them with the correct material I attempted to improve
on the original by using the thinnest available kangaroo leather, about
0.004 to 0.005 inch thickness (having seen the insect riddled state of
the original zephyr).  This was too thick and had enough spring to it
to be problematic, so I got to re-do them all in zephyr.

Cheers!
Roger Wiegand
http://www.carouselorgan.com/