Yeah discpads.com.au don't list the slotted rotors for the rear but you can get them from DBA.
Autospeed list them and you can get them although yes they wouldn't make much difference but I need all the help I can get with braking.
The rotors aren't actually made by DBA either. Neither are the front ones, some interesting information that came from the DBA tour night last week.
They supplement their range by buying in these rotors from Europe. They come from the same factory that makes Brembo rotors(Brembo don't actually make their rotors, they get another company to make them to their specs) thats the same place where these MA61 Front and rears come from. DBA just open the brembo boxes and re-pack them into DBA boxes.
Most of the rotors we are buying from DBA arn't actually made by DBA. Maybe the new supra and soarer they make but not any older stuff, its not cost effective for them.