If you don't want to put in trash your vaccum pump and buy a new one (~45€) because of small and rubber head part ... you can print a new one :)

This is the "dead" part of my vacuum pump:

On the left the old one from Nauticam when it was new and the repared one on the right side (sorry for pictures size, thingiverse make some strange modifications with resizing)...

Please use a flex filament such as filamentum flexfill.