Was looking for a convertible booster for my 4.5yr old. This one checked all the boxes and as a booster rates highly.
https://www.childcarseats.com.au/find-and-compare-child-car-…
Don't forget cashrewards and 8% gift card with suncorp.
[Edit] - not the lowest ever, amazon had a better special back in August (https://www.ozbargain.com.au/node/559161) but helpful if you need something now.
I definitely don’t recommend this seat! It uses the vehicle sash seatbelt instead of a harness for a child that is only 4! Extended harness seats such as a Britax maxi guard are so much safer.
My 5 year old is in the maxi guard pro. They harness until the child is around 8 some can be harnessed until 10 depending on size of the child.