3-D printing is quite the up and coming thing at the moment – although smooth surfaces are still a bit of a problem.  But you can buy some potentially useless items for your layout.  How about N-gauge pigeons?  They come in packs of 121 or 484. (Why 121?  11 x 11 on a sheet, I guess).  Perhaps Duncan could add some to the Houses of Parliament, though these don’t look fat enough for a London pigeon living on a diet of ham sandwiches and crisps.  See http://www.shapeways.com/model/499052/n-scale-1-160-pigeons-set-of-121.html

UPDATE – Only 3 pigeons were recorded on the Houses of Parliament…..