The current parts list for the current kegboard shield can be found here:
http://kegbot.org/wiki/Kegboard_Parts
The shield and coaster can be purchased from here:
http://kegbot.org/kegboard/
As for the flow meter there are a couple of options. There is the Vision 2000 and the
SwissFlow 800. The Vision 2000 is kind of hard to find now, I bought mine from Mike years ago. I know the SF800 can be found, and several of the members have done group buys, perhaps they can chime in on details.
As for the solenoid valve, this is something I've been looking into for about a year now. There are lots of valves out there that will work, however I've yet to find the 'perfect' valve for this application.
Geoffculp has a pretty comprehensive parts list that list just about everything you may need to build a kegbot.
http://kegbot.org/kegbb/topic/186/