You might look at whether it can be rebuilt or not- some are- but there is no in-place fix, mechanic in a bottle that will cure it. When the drip comes out of the weep hole, it's time to pull the pump.
A friend has a John Deere 250 skid loader, and the dealer wanted almost $600 for a new water pump (Kubota's are less than that, thankfully), so he bought a rebuild kit for the pump- less than $60.00. Crazy what Mother Deere wants for her stuff.