It's not able to be ordered through Bottlehead. PB may be interested in custom building you something, but you'd need to work out the specifics with him.
I did have a second one we built with a little bit different input and output configuration. PB should know where that one is at and if it is available.
Yes when I read this post, I realized that there's still one downstairs somewhere. I'd have to fire it up and assess its operational condition, though I don't technically consider myself the owner of that particular unit.