I don't see the point of including magnetic deflection tubes, because obviously they can be very large.
This isn't a complete oscilloscope, but the largest electrostatic deflection CRT I know of was the HP 1321A 21" XYZ monitor.
I haven't seen that one in person, but I do have its smaller brother, the HP 1311A 14" 5MHz XYZ monitor. It's pretty impressive.