I need a Tonneau cover. What kind do you suggest?

I have a 2008 Toyota Tundra and I'm looking for a tonneau cover for it. The issues it must answer are, it must be lockable either by itself or through the locking tailgate, it must be cut proof so someone can't just cut it open and it must be retractable or foldable so I can carry oversize/tall cargo. This is my work truck and I'm tired of people trying to steal stuff out of the bed. I had a Leer camper shell on my Z71 but it kept me from carry large appliances or 4wheelers and other tall items. Please respond with possible solutions including namebrands. Pro's and con's of each suggestion would be helpful too. All suggestions are greatly appreciated.