Generally speaking, there are 2 kinds of Bidet.
1. The first kind is basically a hand-held shower (photo below)

2. The 2nd type is basically a base having a nozzle coming out of it. It is installed on top of the toilet's seat (see photo below.)

According to a Reece (a major plumbing supplies' seller) employee, installing the 1st kind is illegal in Australia. Following is how he explained it to me. He said if the shower hand falls inside the toilet seat, and at the same time a leakage in the water network occurs (possibly meters away from the home, at which the bidet is installed), this leakage point causes a low pressure point, which causes water to be sucked from the water inside the toilet seat into the water network (unless a backflow preventer is installed or the bidet is installed on a different water source than the main water network). Obviously, this causes a major contamination risk to the water network. Please, refer to the link below for more information on the Australian code for installing a bidet.
However, installing the 2nd kind should be OK (provided the landlord's permission is taken and the installation is done professionally.) This kind is available at stores and online. Search on Google for Bidet Seat.
As the case for everything on this website, we are NOT responsible in any way or form for any damage or loss caused by the information on this website. Please, make sure you check with the appropriate authorities and subject matter experts before making any decisions. Please, check the link below for more details on the Australian code for installing a bidet.
https://www.abcb.gov.au/Resources/Publications/Certification/WMTS-Bidet-douche-seats