4x4 = fire extinguisher, UHF, axe, shovel, air compressor, off road 1st aid kit (pays to check expiry dates and refresh every couple of years and replace what is used as soon as), tyre repair kit, sunscreen and 10 to 20 litres of Water.
Personal = 2l camelback, 3 fruit bars and 3 nut bars, enough toilet paper for a couple of 10-100s, PLB, GPS (always mark the vehicle as a waypoint before leaving it), head net, snake gaiters if deemed needed, matches or flint lighter, aeroguard, whistle, 2 setopress compression bandages and a mini 1st aid kit.
I can use the camelback with the detector harness. The rest I use a bum bag sits above the battery and pockets in auscam trousers.
I tend to work an area, then move on, so I could hang the camelback and bumbag on a tree, detect the area and then put back on before moving on. Not so good in heavy scrub sometimes so leave em on.
Obviously this is for solo detecting, if 2 or more people, then not all of the carry stuff may be needed. Or if very close to your vehicle.
The very best thing anyone can take into the bush detecting is - common sense