Car seat with inbuilt harness up to 26kgs.....

[skybie]

We have an infa secure one hun, has the 5 point harness until a certain weigjt, then h harness untill 7 yrs old.
WasOnly $ 180 at baby bunting

[skybie]

Its the infa exceed

[Freya]

H harnesses arent recommended, they are dangerous. Youll be hard pressed to find a 5 point harness accomodating up to 26kg/7 years old without importing (which is illegal).

I would personally recommend the Infa Secure 0-8 Luxi Crown. Google it. It has extended use of the 5 point harness and then converts with adult seatbelt.

0-8 Luxi Crown: Australia's only newborn to eight years child restraint.

VERSATILE
The 0 to 8 is the most versatile of any car seat. Suits the needs of: parents, grandparents, carers, childcare centres, taxi/hire companies, etc. by offering a single solution design.

COMFORT INSERTS
Multi use inserts for baby's comfort and enhanced safety. As baby grows, they are removed, making the 0 to 8 suitable through to eight years old*.

COMPACT FOR EASE OF FIT
The compact multi-recline action means the 0 to 8 in rearward facing mode fits most cars comfortably.

FIVE SHOULDER SLOT HEIGHTS
The 0 to 8 features five shoulder slot heights making it suitable for a vast range of different sized children, from premature babies through to most tall or large four year olds*. It can then be converted into a booster seat for use through to eight years old*.

[Novella]

We have a baby love ezi combo for dd2 it has an inbuilt harness until their shoulders are to tall then it switches over to a booster with seatbelt, it is fairly wide if you have a small car or lots of seats to fit in

[~Kim~]

Tan I don't think you can get a 5point harness for that weight. Reason being that the seats made here can't guarantee the integrity of the harness in an accident at that weight. The safety standards here don't say they have to, so they don't.

[Freya]

If your not keen on the Luxi Crown, the Cargo Marathon is the next best 5 point that has wiggle room for both weight and height. It has 50cm shoulder straps, the highest slots available. My 3yo is 19.5kg and 115cm; still comfortably in the 5 point Cargo and will be for quite awhile. 5 points are tested with up to 22kg of weight so you have until that point before you need to move up to the adult belt/anchored booster combo.
If your needing a booster seat w/ adult seatbelt, the Infa Secure seats are probably the best on the market with a 4 star rating. We have a Vario Max.

Your other option is to import, but its technically illegal.