Can anybody please tell me what this is called (haberdashery I suspect)

[Sallythedog]

I need to buy a couple of these things, larger than the one shown on a raincoat, but don't know what to search for. Not sure how to describe it, in case the photo doesn't properly show. When you pull of the string on the raincoat hood, you can move this metal part to hold the string in place. Hope that makes sense.

Help gratefully received.

A cord / coat toggle seems to bring up what you are looking for. Not sure if that's their proper name

Try googling "toggle for clothing".

It's called a toggle cord lock

Are these any good

They get called a few thingsmetal spring lock stopper, Cord Toggle Fasteners, drawstring cord lock