Finding 4x5 transparency film is pretty difficult locally and I'm not aware of anyone who stocks 8x10 colour neg or transparency. Perhaps someone else might be able to chime in?
For 4x5 Provia and Velvia 100 you could try Lofico.https://www.lofico.com.au/collections/4x5-film
There is also pbarcelona on eBay.
No one has ever been able to clearly explain to me is why Fujichrome sheet film is so much more expensive in Australia than overseas compared Kodak and Ilford films. Provia and RVP 100 currently sell for around US$75 per box.
I hope that is of some assistance Marko but if you need 8x10 colour I suspect you will have to look at bringing in from OS.