Cardude,
Actually,
here is a pretty good overview of what it will take to overhaul the Johnson pump. Compass Marine did a good job on this and it clearly shows what it will take.
Sources for the pump parts are the generator manufacturer, Yanmar if you can positively identify the engine type,
Depco Pump Company, or just get online with the pump model number and see what sources you can find.
Here are some Yanmar parts sources if you are back on the Gulf Coast:
Laboarde Products, Channelview TX, 281-247-8925
Gulf Complete Marine Service, Inc., Kemah, TX 281-334-4417
Y.E.S., Kemah, TX 281-538-9377
Palmer Power, Houston, TX 800-364-4637
I do like the idea of buying a new one and having a rebuilt as a spare. That's what I do for my main, and might do it for the generator next time it needs service.