Might be worth asking in the bookstores in the Grainger market if you get up to "The Toon" much, I'm sure they're got plenty of contacts in the S/H book market. I have heard of "book hunter" type places , you know , "You name it, we'll find it..." but I'm afraid don't have any info on where to start.
yes, the book has gone out of print now, although there seems to be plenty of the other sections on sale. I've just seen the Abebooks.com one for £60. I paid for one for £40 but that's also been sold, so it looks like it's going to be £60, unfortunately. Serves my right for not getting it a couple of years ago