The rack and pinion was way too expensive here in Australia for me to justify spending a huge amount on so I ended up fitting 1/2" roller chain at about $30 for 10 feet length. It's industrial strength stuff so it should last a while as there isn't too much force on it.
I wouldn't recommend anything under 18 teeth for the sprockets as there is significant cogging under that but over 18 - 20 teeth it seems to be negligible and pretty smooth as can be seen in the video.
Let me know your thoughts on how it turned out. :-)
Be very critical if you wish....... I am pretty thick skinned.
Rich.