Definitely a jump starter, I've got one of these
https://www.ozsale.com.au/product/O...es-up-to-10-0-Litres/s/_85t6bEuj0_Kf2rmEoOIXg
I have a 200 series landcruiser (4.5lt V8 Diesel) I've used it on that and it started which is pretty amazing as it uses your flat battery to start the car, so you don't have to keep it charged as there is no internal battery to charge.
I also carry a Lithium Gooloo GP4000 battery pack also, there's no way I'm getting stranded with a flat battery
I have an Engel in the car so have a fold out solar blanket that I put on the windscreen (put solar reflector under it as heat can turn laminate in screen opaque) to keep the axillary battery charged.
Other items in the car or carried, plenty of water, Staminade & food + big bag of nuts & biscuits (just in case you have to walk out) small first aid kit, eye rinse saline tubes, hat fly net, spare battery for GPS & torch, zip ties & superglue (for bush fixes), gloves, Tyre repair kit & compressor, RYOBI rattle gun (awesome) 5 Watt 2 way radio and most important thing is a big bucket to put the gold in