im also a lefty. i just make life easier on myself and learned to safetly control a blade wtih my right hand.
i say stop being different, and just ride your blade in your right pocket and use it with your right hand.
it opens up so much more options, as to which knives you can own.
but if you must, locking mechinisms really arent that hard to disengage with left hands. so if you absolutely must have a left pocket ride, get one and just deal with the lock.