Sunhat for the big headed.

[TheTeaLady]

I need a wide brim sunhat but everywhere I try them on, they're too small.
Can anyone suggest something that I might be able to get onto my outsized noggin?
It must be able to travel all squashed in my luggage.
I don't want to be wearing a sports cap - I want to channel Joan Collins.

M and s do 2 hat sizes. How big is big? Think most shops work on an average of 57cm circumference.

Thanks! I hadn't even tried Marks.
Shows you how dedicated to the art of shopping I am.....