It would probably cost about $1200-1500 for a basic single axle 1500kg trailer running gear kit, non braked. From there you are only limited by ability & funds to make what you want. Those Aussie Offroad trailers usually have independent coil suspension as opposed to leaf spring so there's a chuck of $ for a start.
Elite Trailers in Chch imported some camper trailers awhile back that were a cancelled order for an Aussie customer, direct out of China. Not sure where they ended up but you could luck upon something secondhand.
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