SAAA doesn't actually have W&Bal people (who will come weigh your aircraft), but some of our members are personally a CASA appointed Weight Control Officer - WCO - nothing directly to do with SAAA.
Ceri (it's Welsh) - from Sydney area I think - she advertises in Aviation Trader, as do a few others around OZ.
CASA will not release a list of all the WCO's that THEY appoint. There are more around than you might think, but finding them is difficult, they don't advertise, probably because it's something they do for their employer and it's not an activity they need to run around getting involved in for the general public. They might weigh an odd aircraft that is on their home airfield.
As an SAAA member, I don't know what the RAAus rules are about who can do what with weighing. But I know what SAAA members cannot do. SAAA members only weigh their own aircraft, not anyone else's. Many SAAA members are also RAAus members who fly both flavors aircraft.
I and many others try to help any RAAus members who might ask us something, and I find usually I have to just refer them back to their organisation RAAus because their question is outside our scope. We get calls from people who confuse SAAA with RAAus (or SAFA - ex HGFA) . Quite common, usually from people who have bought some plane or are considering buying some plane. We just point them in the right direction for their query and they are happy for the help.