You are not dealing with a short circuit, you are dealing with an intermittent open. There is a flaky connection somewhere in the power feed circuit that is common to all these accessories. I would start with the fuse.
You can determine that a fuse is bad by looking at it, but you cannot always determine that one is good by looking at it. Sometimes it will be broken and intermittently make continuity. I would find the fuse, remove it and tap on it while doing a continuity test. If it occasionally does not make continuity while tapping on it, replace it. If this happens, make sure you throw the fuse away to prevent it from driving you nuts later on.
If you find no problem with the fuse, trace the connections from the fuse and wiggle them along the way to see if you find a point where wiggling it makes the accessories go on and off. If you do, you have found your problem.