I think Bond Roll Bars do a half cage (4 point) and also a full cage (6 point? with removable intrusion bars). It was awhile since I spoke to them but I'd say they still do it.

Hey Guys
just wanted to know if anyone is running a street Car with a half roll cage.

Can roll cages be used in vehicles as long as they
are designed and constructed properly?
Roll cages can be used in vehicles provided the
installation meets the applicable vehicle standards.
Installing a roll cage has the potential to affect one or more
Australian Design Rules (ADRs), in which case
certification will be required.
The relevant standard is the requirement in Clause 21 of
Schedule 2 of the Regulation that everything in a vehicle’s
construction and operation must not pose a danger to any
person.
Four-point roll cages can still meet this requirement,
however six-point roll cages cannot because the
configuration of a six-point roll cage creates a rigid item
directly in the head-strike area and obstructs the driver’s
vision through the windscreen and adjacent side windows.
A six-point roll cage may be installed in a vehicle if the
front part is removed when the vehicle is used on a road or
road-related area.
Guidance on the fitting of roll cages can be found in
Section LK of VSB No.14.

Not really a 4 point sorry but anyway