The buttons may be at the wrong side but unless you go with microsoft Laser 5000 or Laser 8000 no other uniform mouse that I've seen that can be use for gaming by lefty.
I am a right handed person so I would chose one of the first three I mentioned above, My wife is a left handed person and she won't use any other mouse unless it has the same design and buttons like the microsoft.
I feel your pain as a left-handed gamer. I remember the first time I played UT3 and found the switch weapon hand option... I am way better at headshots since being able to 'see' the gun on the same side as when I shoot in real life.
I use a Logitech LX-8 and a cheap forgot the namebrand Rage FPS keyboard, both 'unisex' but they work well. I still get jealous when I pick up a buddy's 'made for right hand' gaming mouse and it feels awesome, well except for being in the wrong hand. Also you can count out any left-handed quality flight controls, I currently use a Saitek AV8R and Cyborg 3D with some homemade rudders I made from real rudder bars and an old broken joystick.
If any other southpaws have any other solitions please share