As has been mentioned, the monumental biography of Paul Clayton by Bob Coltman is now available (Scarecrow Press),
and his last recordings for Monument (2 LP's and 4 additional songs only on 45rpm) have been issued
complete on 1 cd, also now available (OMNI, Australia). It is available in the US.
http://www.worldwentdown.com/omni/omni120.php
Best wishes, Thomas