Handlebar stolen along with gear shifter and brake triggers. What to do how much am i looking to spend?
I don’t know about Australia but here in Austria a cheap 9/3 speed Shimano Alivio combined brake lever + shifter can be had for 18.95€. Add another 20€ or so for the handlebar and you end up around 60€ for the repair.

This assumes your bike uses mechanical brakes and 9-speed MTB gears. 10 speed will be more expensive. Hydraulic equipment and refilling hydraulic brakes will be more expensive as well.