Wanting to kitbash some chaos dwarfs with big hats

As it happens, a bell shape turned upside down is a good basis for a hat - my only trouble is I'm having a hard time finding ones that would be a suitable size. The lower diameter of the bell (where I will cut horizontally) needs to be about 6 or 7mm across.

The closest I can see in size is the one from the nurgle plague drones kit but that's hard to come by and needs putty work to fix the sculpted corrosion