I third the rebuild idea...

And here is how to do it cheap....

Drive out to the nearest farming community town... make sure it has a least three tractor dealers...

Drive an old pickup there... and take the water pump in to the local machine shop.., tractor shop, alternator rebuilding shop... and don't even tell them what it came off of... ask if they can rebuild it.... tell them you are not in a hurry. Old tractors would not be running if we had to find " new" on stuff like this that wears out regularly ( every 15 years )....

You may think I am kidding ... but I am not .