If you want full freedom of movement, you should opt for a wireless mouse such as this one. While most computer mice have two buttons (and maybe a scroll wheel), this one has six.
From OnBuy
Hama Vertical, ergonomic EMW-500L" left-handed wireless mouse, 6 btns, blck
Priceless Computing
Hama Vertical Ergonomic EMW-500L Wireless Optical Mouse, 6 Buttons, Browser Buttons, 1000-1800 DPI, Black (Left Handed version)
This product is also available at 1 unverified merchant.