Places to go, that I can think of not being in Ausand all, would probably be Supercheap, Repco, Mitre10, or maybe Bunnings and for brands (of bondo/filler) the two I know of are CRC/Mendent (which is normally in Repco and Mitre10) and Septone which I've found in Supercheap. Not sure what brands Bunnings would stock but they're bound to have something.
I think pretty much any major hardware or automotive stores should have something,resins I'm not so sure of brands but I know Repco and Supercheap both stock some (usually small repair kits).
Also welcome

I'll update the front page again... been a while since this topic was up here.