I'm sure demon tweeks stock something suitable or if you fancy a budget version, try and get the dash out of a Tipo DGT - they were really cool in their day.
Found some schemes for do-it-yourself kits, so perhaps I will try them.
While searching I found something that's also an option which I'll consider: http://www.minisystems.nl/index.php?main_page=infopages&pages_id=29
Site is in Dutch but the pictures speak for themselves
I just don't want Windows XP in my car, so I will probably use Linux.
Just stick a GPS-mouse to it and find a programm which adapts a cockpit
Oh, the possibilities