DVD is available
I was looking for this on DVD ever since Kill Bill Volume 2 came out.
Finally found it:
http://www.cdjapan.co.jp/search.html?type=GC&word=Navajo+Joe&restrict=DVD&step=50&sub=
It's on Region 2 from Japan and an excellent transfer.
I was surprised by how good it actually is. It's probably my favourite Spaghetti Western behind all Leone's films. Plus, the soundtrack rocks.