The April 2012 AMRM has a review of a laser-cut church kit in N scale, but the same kit is available in S scale from American Model Builders "Laserkit" range. The kit for the "Crossroads Church" is for a small weatherboard church, typical of many small towns both in Australia and USA. The AMRM reviewer added a corrugated iron roof to his N scale church to make it look more Australian.
Here is a photo from the manufacturer's web site.
The same company has quite a few other structure kits in S scale and, although some are clearly of US prototypes, others would be at home on an Australian layout.
According to AMRM, Model RailRoad Crafstman in Sydney are dealers for LaserKits, but I don't know if they stock or can order the S scale kits, and their web site does not provide much help.
I also noticed in the April 2012 Model Railroader, another US kit by Frenchman River Model Works for a barge. Although this kit is HO scale, the magazine notes that is also useful in S or O scales as real barges came in various sizes. Here is a photo from the manufacturer's web site.