I will follow Colin's advice to finish the break.
Just spoke to a plastic repair company here in Amsterdam.
I will go there on Tuesday to decide what is the best way to (try to) repair the breech.
Perhaps plastic welding will be possible.

I still think the Innova was Sharp's best design.
I have 8, and this is the only one with a (big, lol) problem.
All from the eighties, all working perfect. So light and compact, big smiles every time.

The manual is indeed clear that one must hold the breech whilst pumping!