I know of a solution for you but it may be a bit over kill. I have one but only used it once as I need to add a multi port serial to my system.
I have 5 cameras and two monitors and video capture that I use with it.
It is a 16x2 matrix switch unit. Serial controlled. 16 input to 2 output, with 2 additional bridged to the output. Farly cheep for a matrix video switch.