Zephyr skin is available in Europe from Herzog in Germany.  They supply
in three thicknesses and I have found it to be excellent quality:

  http://www.lederfachhandel.de/orgelbauleder/leather-for-organbuilders/ 

Zephyr is also available in the UK from Russels Leather:

  http://www.russels.com/pipeorgan.shtml 

John Farmer, UK