I've shot lefty all my life. I just curl my hand around the trigger guard, so that my trigger finger can push off the (right handed) safety as I raise the gun to my shoulder. In the army, I used my thumb to do so with the M16, and still beat everyone else to the hit. I dryfired practice every chance that I got. See, I knew enough to take some Hoppe's #9 and pieces of sheet, with me to basic training. While every one else was trying to "clean" their rifle with white oil, I was already done, and practicing with the rifle.
My squad leader knew what Hoppe's smelled like, and knew I was into guns. He came out of his room sniffing, and demanded that I give him some! Since he could stick me with various unpleasant "extra duties', I had to cut him in on the good stuff.
Millions of people all over the world, have had to deal with the horrendously slow to manipulate safety on the AK, while they are actually in combat zones. Almost to a man, what they do is keeo a rd chambered and the safety "off". They deal with safety issue by rigorously not having their finger inside of the trigger guard, unless firing is imminent. So for your once-in-a-lifetime Home Defense situation with the shotgun, you can do the same. For hunting, just do as I do with the safety.
Left handed guns not only cost more, but they are VERY hard to sell later. You''ll eat a lot of money if you do. Most buyers won't want it at any price.
I of the school of run what you are comfortable with. Hunting wise I can and have many times held my own hunting with guys shooting pumps or autos Hell the shotgun I've had the longest according to internet experts is the biggest P.O.S ever biult a smith & wesson 916 $125 new in 1975 in 81 alone I killed $2500 worth of fox with it Neather remington or mossberg would have sold 10 million plus if they were as bad as the internet experts claimed 
