1: THAT fortification WASN'T a "
GW fortification". It was made by a German company (not under licence, it was that company's product) and up until about 10 years ago was still available. The staff at my local store weren't allowed to say where you could get one (if they knew what it was) because it wasn't a
GW product. It's made out of a hard foam, though. So it's reasonably tough and still light.
GW just happened to have one (it showed up in several codices over the years).
That company still make something similar (the design got changed over 10 years back, though).
Edit: Ziterdes.com is the company.
Their current Bastion is this one:
http://www.ziterdes.com/buildings/casteles-fortresses/bastion-15-76-x-11-03-x-8-27-6012055.html