Last time I checked, Midnight Marquee still has My Autobiography/Past Forgettings for sale.
http://www.midmar.com
You can also get Tall, Dark and Gruesome with a signed bookplate if you're interested. Same for Michael Ripper's bio.
I tend to like that publisher's books.
It took me a long time to track down a copy of Cushing's book (the Midnight Marquee edition) but it was well worth it. There are some truly wonderful and surprising stories. Even if you aren't that familiar with Cushing (and I wasn't at the time) it is an excellent read.