Anyone knows whether can bring buckwheat husk pillows for children to use into aussie?

Yes you can bring them over to aussie. Alternatively, you can also purchase it from aussie to save yourself some luggage space! You can also try making it on your own. https://www.bio-oz.com.au/buckwheat-hull-pillow The above website allows you to purchase the buckwheats and have it delivered to your house.