Belkin used to sell plug-in smart switches in Australia but withdrew them from the market a few years ago. My guess is that their lawyers were concerned about liability if a switch causes damage or injury.
They need a WeMo Bridge to work with Homekit. This can be bought online and uses USB power so works in Australia . I have a couple of WeMo switches and Bridge working great with Homekit but I am concerned that I cannot replace them if they fail.
Regarding lights, I use LIFX lights that use wifi for Homekit connection and don't need a bridge. Luckily they remember the last setting when switched off at the light switch so, provided I remember to have them "on" when I switch them off at the wall switch, they will come on again when switched on at the wall switch. Homekit can''t see them, of course, when they are switched off in this way.