Tisha,
We are planning a VSG up to and beyond 6 GHz, but we do not presently have anything, and probably won’t for a year or more. For now, depending on the accuracy and linearity you need, you might consider upconverting the VSG25A output (e.g. using “evaluation kits” from Analog Devices), either using an image reject mixer or a filter to reject the image. This might be an acceptable alternative to waiting for a VSG60A or VSG200A.
Of course, there are also other affordable vector signal generators (e.g. used R&S or Agilent generators) that might provide a faster, more accurate and traceable alternative to a DIY project.