Just got a KCS-96 chassis set

[Electronic M]

If you happen to have an audio generator or a low frequency RF generator with several volts of output you could that as a signal generator. It won't put out a standard pattern but you'll get black and white patches (whether they form spots or bars depends on the instantaneous frequency difference between them and the sweep). Hell, if the set isn't hot chassis you could capacitively couple 6.3v from the heater into the video amp grid....if the hum bar gets through you know that the amp is passing signal.
There's no perfect substitute for the right test equipment but if you're smart and desperate enough there's often some workable options.