There is a possibility that a cheap simple fix could get a wiper vacuum motor working and is always worth the try.
Remove the vacuum wiper motor, pour or inject approx a couple/three table spoons of motor oil down the vacuum port into the wiper motor. Shake the motor around at all angles in order to get the oil to coat as much of the interior as you can.. Allow it to sit over night. reinstall it and try it.
I did this to my 49 wiper vacuum motor a little over 6 years ago and the vacuum wipers have worked ever since. They didn't work before I did this. To give a little background on my 49, it had sat non-running since 1969.....
It may or may not work for you but giving it a try only costs you a little elbow grease and a little motor oil.
Good luck
