The filter cap that you are trying to replace, is called a computer grade electrolytic. If you can find a new one, it will probably not be the same size and will probably cost $30 dollars or more.
I would suggest that you replace it with a more common snap-in style cap that is cheap and readily available. There will be two problems with this approach, one, the new cap will be smaller so it will not fit into the existing clamp holder and two, the cap will not have screw terminals so there will be some work at either cutting off the terminals and soldering the wires to the new caps leads or adding screw terminals to the new cap.
I've seen people just glue new caps to the chassis with silicon or use plastic plumbing pipe adapters to fit the new smaller cap into the original cap clamps. I've also seen people use terminal strips to set up a point to point style mounting system.
Whatever way you go, I'd just replace both of the caps so that both sides of the power supply are equally filtered.