We just picked up a brand new trailer yesterday which is made in Sydney and was custom assembled for our needs with a high hinged roof giving us 590mm inside clearance and gas lifters on the lid. We had it arranged through a middle man in Newcastle but since you're in Sydney, it could go direct.
As a guide to price. Ours has the roof mentioned above plus it's 7' x 4' with checkerplate floor, ladder racks, and 1500mm drawbar. Our price was about $1850. Standard trailer without top was under $1000. Seems strongly built. Their website is pretty sad but fortunately, website building isn't necessary to build a good trailer.
But you can get their contact details from their website: http://www.sydneytrailers.com.au/
Our trailer for the price looks similar to this but without 4x4 tyres or jerry can holder. This is one made by Sydney Trailers.
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