A few suggestions of what I like to take.

A camelback. Trackers will normally carry water for the client. However I no longer will share a water bottle having zero interest in sharing saliva with people who have who knows what diseases. I also like to sip water when walking long distances. Easier than stopping to get a canteen out.

A belt knife. Un-necessary but de-riguer.

A multi tool knife. Necessary for all sorts of things.

A good hat for the sun.

A mosquito head/face net. More than useful during a siesta if bugs are insistent.

Good binoculars. Trackers have excellent vision. Try to beat them to spot things. Sometimes, rarely, one can.

BTW some PHs act like all you need to do is pull the trigger. Not even that with some. My attitude is I only have to hire them, because it is legally required ... and for a bit of local knowledge, language translation, some trophy judgement, local countryside and game location knowledge. I could however hire locals, get a vehicle and camp gear, acquire access etc and DIY. It might just take more days. But a hell of a lot more satisfying. But of course it is a monopoly shop.

A good day pack. To carry small stuff in. Or a bum bag. Again some PHs think a client shouldn't carry on. It can also be left in the vehicle for access when in the vehicle.

Bug repellant.

I now seem to sweat more and carry hankies to wipe my face. I may try a shemaugh or Brit style very light scarf for wiping the face. IF it is not too hot around the neck.

I take a good Digital SLR camera plus a long zoom lens. Others might take a small digital pocket camera. If I had the second, I might take both. The pocket camera is easier got to on the walk. And also good for scenic photos. I don't take enough of these when actually hunting. My SLR rides in a Loewe camera bag.

You should be able to walk long distances in your boots. And preferably they be somewhat quiet for walking.

I carry a good small torch as well. A headband will allow it to be used hands free.

I like takedown rifles. So they can be transported in a smaller gun case and even in the bottom of my duffel in country. No one needs to know you have a rifle. Check in th gun case separately when flying.

Take a soft gunbag for the rifle when hunting. If I am using a long gun case, I take out the padding and put the gun in the soft gun bag in the hard gun case.

Other stuff when I think of it.