As August 13th is International Left-Handers' Day, a nice present would be a numpad and mouse button fix. Can you make it happen?
I have actually heard of southpaw mice for sale...and keyboards-- you can buy one with a detachable numpad which can be plugged in the opposite side of the keyboard if you like...;) Good luck!
If you are serious about southpaw gaming, doing it in hardware is really the only the way to do it, imo. Then, no worries about individual games or other software packages.