Well guys I found this awesome 5" 1/8 Turn-lock inspection port from Beckson. Its got a unique design. It locks in without threads and the screw on top completly covers any screws and protects port from any leaks from the top by eliminating the seam where the traditional port screws down. It even looks more like a factory installed piece. Here is a picture.
http://www.pridemarine.com/showimage.cfm?image=Beckson%20DP50%2DW%2Ejpghttp://www.pridemarine.com/images/watermarkLarge.png
http://www.pridemarine.com/showimage.cfm?image=Beckson%20DP50%2DW%2Ejpghttp://www.pridemarine.com/images/watermarkLarge.png