It appears Vol7 and 8 are both not in print.
Good thing I bought them up to 11(?) so many years ago.
I had that problem with Naussica, I was going to buy all of them, but only volume 2 was out of print everywhere. So I gave up and DLed it. English licensers should be required to keep printing, or they can go fuck their copyright protections (not that I cared too much to begin with).