I do not have a spare gear case or water pump at this time. You might try
Tom Theurwactchter at 920-923-1827 or place ad on AOMCI site.
Not that I don't have parts left over from prior projects,just
not the parts usually needed. I do have the brass water pump coves
and drive hubs as well as some water jackets, reed block, cylinders
and some pistons some more iffy than others.
I have also a rebuilt single powerhead
Not in the parts business but if you need ask me.