I've used the the Rick Young bino harness and prefer it for "under arm" carry on my two SA trips, plus for birdwatching, in that fashion. Binoculars used were Zeiss Victory 8x32 and Conquest 8x42, good with both. Use them until it's time to set up on the shooting sticks.
Besides my binos, I carried a spare loaded rifle mag, cell phone for pics, small notepad and pen for notes, a Gerber or Leatherman multitool (great for removing spiny cactus pads)and occasionally a bottle of water in my cargo pants. And a zip lock baggie with TP or wet wipes, "just in case". In the truck had a small bag with glass cleaning kit, smokeless tobacco, chewing gum, ibuprofen and allergy medicine, etc.