Time of flight mass spectrometer (TOF)is just a mass analyzer. First,In terms of ion source, there are two standard ionization methods: MALDI and ESI. Before you make your decision, you should determine which type of ion soure you are going to use. Second, there are also basicly two types of design of TOF, one is linear TOF, the other one is orthogonal TOF.
According to my experience, there are some companies such as Sciex, Waters, Bruker and Shimaduzi selling all kinds of TOF instruments. You can check their instruments on the web.