What is your choice?
1) Sonic Youth/Brigitte Fontaine CD/DVD
Fontaine is on a new label so perhaps it will be possible now...
2) Sonic Youth/Takehisa Kosugi studio session (1999)
3) Sonic Youth Filmworks box set
(Released stuff like Made in U.S.A. and Demonlover and unreleased stuff like Things behind the sun and Nudist Guerrilla).
4) Sonic Youth/Mats Gustafson/Michel Doneda/Jean-Marc Monterra (2007)