Plunger...

Correctly sized and shaped plungers are very difficult to find.

Most plungers these days are bell-shaped or flattish. This one was found while on holiday in Tenerife.
It has the correct hemispherical profile and is a rather pleasing five-plus inches in diameter.

Unfortunately it has an inner 'lip' that the originals didn't have.
It's not perfect but it's much better than a lot of plungers out there...