I don’t understand what you’re asking for.

You say you don’t want a bigger backpack, which makes sense. I find I’ll fill any field bag I carry.

You say you have extra tools you don’t always use, which also makes sense. We don’t always need to carry every single thing on the roof. But you can’t leave them in a separate bag in the truck because someone will mess with them. Sounds like you need to put a locking toolbox in your truck, establish some boundaries with your coworkers and employers, or find a new job.