I'm a lefty. I shoot beretta over-unders that I have had steam bent by a Belgian gunsmith near Montreal. It only cost me 150$ per gun to have it done, which included the measuring etc... and it made a huge difference to my shooting. They both shoot where I look. When I miss it's due to lead/follow through. Operating the levers is very natural - no issues there. My advice would be to find a gunsmith who can do this well, and then just shop freely for a shotgun that you love, then have it steam bent for drop and cast, and have the stock cut or shimmed for length of pull. In my experience, you won't regret it.
Dave