I thought I'd write a quick update since there has been a lot of interest since this project was featured on Hackaday.com (http://hackaday.com/2016/05/01/upgrading-a-20-year-old-pda/)
I'm really happy about that, having people showing interest in your work is always a boost :)
Anyway - several people have asked me about making the keyboard adapter available. While everything you need to make one is on Github, I fully appreciate that my design is pretty challenging to put together for people with little or no experience of surface mount soldering.
So I'd like to hear from you - are you interested in getting a pre-built and tested keyboard adapter? The adapter looks like an Arduino Leonardo to your computer, so think of it as a tiny Arduino board with a connector that fits the Psion keyboard. While I'll make sure it works properly before shipping, I won't be able to provide much support or any warranty. This is mainly meant to help a few more people getting their own projects off the ground.
Comment below if you are interested!