For those in 'civilized' parts, try your local Pet Supermarket or garden Center's Aquarium department for dragons and greco-roan archways, pagodas and Buddhas too. I also found some small junks/sampans (not quite sure of the difference).
It seems people who keep fish in aquariums also like to cover the bottoms with statuary etc. They are in some kind of resin/polystone and pre-painted but improved by a repaint. They can also be found in Aquarium suppliers on the web for mail order. Prices vary according to size, from around a fiver to £30-40 but still good value when compared to some wargames pieces (especially GW!).