For field gear I use a large duffel bag. I thinks it's an Israeli military bag, it's made of canvas and has a bunch of hooks and clips on the outside of it. I use a similar bag for a range bag when I go shooting. It holds the tool and spare parts box, radios, and fuel and I carry the trucks. For spare parts a few of those tackle trays for fishing work well. For fuel I have 3 fuel bottles and just fill as many of them as needed to bring with instead of carrying a large jug of fuel around. The Mad Force I have can be strapped to the bag if I need to as well. I limit how much extra parts I bring out to run. Usually I carry just the essentials like extra screws and nuts, spur gears, batteries, etc. Anything that would take me longer than 30 minutes to replace ends my day of running.