Leni Sinclair has just produced a signed limited/numbered edition of 50 of the Dialogue '68 Poster from the 1st Unitarian Church gigs in 1968. The only original I've ever seen sold was torn and had yellowed tape all over as well as missing large chunks in all corners and that sold for US$900!
Poster size is 24" x 30" same as the original, on heavy, glossy paper. Leni is selling these for $50 + postage (for UK postage is $20)
If you're interested email Leni at firstname.lastname@example.org