BB07
Hopefully this post isn't too helpfull or factual, as I would hate to spoil the flow of the thread so far
Try Ad-Astral for the B1900, Maroomba and the RFDS for the B200 and Avwest for the Caravan. Outside of Perth its Karratha Flying services for the C90 or a few operators in Broome for the Caravan
They all have their own websites with recruitment pages.