I can't find a suitable "Walker" at all at the moment.
For the FFL I will be using something fairly small, as they have what is designated a 'light' walker.
I am thinking of something like this, converted to hold a 'driver' and with the correct weaponry, of course:
http://www.trollandtoad.com/p88951.htmlYou could always just get started and do the infantry figures first, mate.
That way you can get playing straight away.
You can always go back and add the walker when you have found something suitable.