I am a member of the British Railway Modellers of North America. You may want to start at their web site, http://pages.ca.inter.net/~brmna/. Click on the "BRMNA supplier members" link near the bottom of the first page. Most of these supplier members are really nice folks. If they don't stock these buildings, perhaps an email to one or more of them may at least allow you to find out whether they can order them for you.