A Connexions QL Centronics printer interface, connects to the serial port I believe. Also, a QL-9pin serial cable.
All in for £50+p&p.
They are pictured above and to the right of the QL, which is available separately (as is the Trump card).
FS: QL parallel interface
Re: FS: QL parallel interface
If you'll include this in the book package quote, I can get you some closure on this one too.