APM 2.6 upgrade to PX4

Hey,
I have used the APM2.6 a few years ago on several Quads with great success.
My Quads have gathered dust but I’m now looking to get back into it.
I’m guessing the go now is Pixhawk 4.
I have a lot of hardware for 3S, ie: Batteries, ESC’s etc.
I’d like to reuse the hardware I have but I’m also adding a T4-3D Gimbal.
Can you advise my best options on the Pixhawk 4 version and cost etc ?
I dont want to spend $200-300AUD on the flight controller if possible.

Thank you.

Regards
Matt

Hi @motionman welcome to the forum!
Here is one option: