If I do have one, its one I took out of something. I don't use circuit breakers, because I think they suck. I've had too many problems with them tripping for no reason, and I've seen more than a couple refuse to trip when they were really needed.

Go with a fuse. Its not that tough to pull one side of a fuse to work on the system, and provided your wiring is sound, blowing them should be very, very rare. On that rare occasion though, I'd rather trust my car to a fuse.

Toby