Does such a thing exist. My google-fu is weak now.

I want something that attaches to the factory bolt release and extends straight back, or down and back, making it easier for my left index finger to manipulate.

this would work, but I want it further down and back and not so big

I didn't think so. Maybe I'll bend and cut a BAD lever, or have someone make me one locally.

That would have been my suggestion. I think modifying a BAD lever would do what you want, but it might not be pretty.