What I am talking about is a device used to remove electrical interference that is being conducted by a wire.
A feed thru capacitor is about 1/2 and inch in diameter, about 2 inches long, and has mounting tabs on one end. There is a threaded screw opening on each end. These were originally made for aircraft and military use during WWII. They can still be purchased at places like Aircraft Spruce, Allied Electronics, DigiKey, and other electronic suppliers.
A good value for your application is a .1mfd at 600 working volts rating. And yes, they will work with 110 or 220 VAC.
The attached picture will be worth a lot more than words.
Click on the picture to see it at just about actual size.
George