A simple male-female adapter that swaps the mouse button lines would be very simple to make and there's really nothing that could go wrong with it.
I've actually never had a problem using the default button assignments with either hand.
I guess I just don't associate left click behaviour with my index finger when using my left hand.
While I'm not ambidextrous, I do use my hands interchangeably for a lot of things that most people only do with their dominant hand. My left-handed writing looks pretty childish, though.
