I'm currently obsessed with mason jars. In my attempt to not have anything country in my house, these little buggers are the only thing that have made it through, but in a modern way.
Cutting the metal lid is the hardest part and you can try to use scissors or a sharp kitchen knife. Punch a hole in the center and the keep stretching it until it is large enough for the pump to go through. You can use a pump from any soap dispenser you like or buy one that is more fancy. If it is too long, cut off the bottom to the height you need it. The widest part of the pump will cover up the part of the lid you make the hole in so it doesn't have to be perfectly circular. You can make it fun by swirling different color soaps or use it for lotion.