Can this hand water pump be fixed?

When you say there is no innards have you had it apart, the only thing inside would be a check ball in the bottom and the plunger/piston on the bottom of the handle if that is there and it is not ate up with corrosion it most likely can be rebuilt. If the seals on the plunger are dried out it will feel like it is empty inside. It works just like an old hand pump on a well for sake of a better description.

Yes any good hardware store most likely will have a selection of universal O rings and seals that will repair most things. I usually measure the old ones and then match as well as possible. When sizing an Oring you should measure the inside diameter, the outside diameter, and the width of the groove that it sit in this information will get you close to what you need. Many times you will get a smaller size and stretch it on, this will tend to change all dimensions. often it is a trial and error thing. A real old pump might have a leather seal and these can either be made from leather ,rubber, or plastics. Give it a try then let us know how it went.