Nothing except a dummy, a sleep sack, and a fitted sheet.
Nothing in, on, or attached to the sleep space.
Baby should be placed on their back for every sleep until they are a year old.
Even if they can roll, continue to place them on their back.
Whatever position they get themselves into after being placed on their back is safe, granted they are not swaddled.
The only suitable sleep space is a cot, crib, bassinet, or portacot.
Find a cot that meets standard AS/NZS 2172.
Bassinets are not regulated in Australia, so find one that also meets US standard
No loungers, swings, Dockatots, baby nests, or adult beds, None of these are safe for sleep (1).
Drop-side cots are unsafe.
Never make alterations to a cot.
Task Force on Sudden Infant Death Syndrome. SIDS and other sleep-related infant deaths: updated 2016 recommendations for a safe infant sleeping environment. Pediatrics. 2016 Nov 1;138(5).