Switched Power Source in Engine Compartment

[evanevery]

Anyone know of an easy-to-access switch power source (wire) in the Engine Compartment?

My device only needs about 8ma but it should be a switched source. I've been poking around but its a bit tough to find any obvious choices. I know where the fuse box is but I would have to modify the cover or the base to be able to pass a wire through it. I'ld rather avoid that if possible....