Bright Suns Debbie! Thanks for visiting planDisney.
I'm sorry to hear you're having difficulty finding a way to get your lightsaber safely back to your home planet. Airline rules do differ, and it sounds like it's left you in a bit of a tight spot. Did you try breaking down your lightsaber? While a fully assembled lightsaber measures just over a meter, you can disassemble the lightsaber into a hilt and blade for the flight, which might assist in making it fit into your luggage.
While Savi's Workshop - Handbuilt Lightsabers and First Order Cargo in
Star Wars: Galaxy's Edge can ship internationally, I understand you won't be on Batuu in Disneyland Park on the final day of your magical visit. Regardless, last I checked, Savi's Workshop couldn't ship to Australia. This is a dilemma for even the most powerful Jedi! I apologize for that.
My best suggestion is to either take a car service or make a quick walk to a nearby shipping center location, where you can box and ship your lightsaber home. A quick search showed several nearby locations for different shipping companies.
Safe travels and may the Force be with you.
Elizabeth