Onan Water Pump
You're absolutely right, the Sherwood pump is the G702. It looks exactly like the one on the engine and some on-line sellers list the Onan part number with the Sherwood part number.
I replaced the original Onan pump with the Sherwood some years ago.
It has a one piece casting instead of a detachable end plate.
I thought its construction may help to extend the life of the impeller.
At that time I also changed to run dry globe impellers....they didn't make any difference...the impellers where still failing at around 170 hours.
But at the last change I put in a standard impeller and it's up to 240 hours now!
Is that just luck? I don't know...I don't think anyone else does either !