I don't know about your fixture, have you tried googling it in Aus, then contacting them. I have lovely American leadlight set of lights, wired for Aus, I bought them in Drummoyne, Sydney.

When I started doing reno's, that was one of the first things I wanted to replace but the cheapest quote I could find was a touch under $3000 and that was from some random guy from Gumtree that I could barely understand. Everyone else looked upwards of $4000 and that's just for installing the new gyprock ceiling. I had plenty of other things that I needed to do the place, so I quickly ruled that one out. But now after living there, I don't even see the vermiculite anymore. I'll just try and work around it. My thoughts now are to... 1) Remove the ceiling fan. Get a pendant light (either 2, 3 or 4 from my very first photo). Keep the bar light. 2) Replace the existing fan with something more modern. Replace the oyster light with an understated ceiling mount fixture, or just keep the oyster.

Your could install an offset pendant. Draping the wiring over a fixture in ceiling to make the pendant central.

The second look like they are designed for stairwells so I'd be a bit wary about using them up higher as the light might be a bit "spotlight" and not diffuse enough. I think both styles work with your house design