Walter is correct. John Betts and Craig Matthews cornered the world's remaining supply of Z-lon back in the 80's. This is how it was originally packaged by John Betts:

This is amber next to golden ginger Z-lon from Umpqua:

...and this is kinky light dun Z-elon from Umpqua:

Blue Ribbon Flies and Umpqua are the ONLY two sources of Z-lon. BRF does their own dying which differs a bit from Umpqua. I like to be standing in their shop when I purchase Z-lon from them. Here is some info. on their Z-lon types and colors: