Metal cup washer 270

Hi

Has anyone found a source for the part labelled metal cup washer for 154 on a tilley x246. I have one missing this piece and can't seem to find it on any of the normal spares sites.

Thanks

 

Try The Base Camp
Tilley lamp spares
but "metal cup washer" is an unknown part to me.

Erik

 

Its actually from this diagram as part 270, but here's a picture of the piece I'm missing in case there's another name for it.

https://www.base-camp.co.uk/exploded views/Tilley/guardsman.jpg