Wanted urgently: fancy dress policeman's helmet

Hi folks,

I am in desperate need of a British policeman's helmet (the old-fashioned proper pointy helmet-type, the more old-fashioned, the better) for tomorrow night's Come and Sing The Pirates of Penzance at St Paul's church.  We did have some hats coming, but they haven't arrived in time.  If anyone has a helmet that I could borrow, have or buy and that I or one of my colleagues could pick up locally tonight or tomorrow morning, I would be extremely grateful.  It needs to be capable of being worn by an adult.  If you have more than one, even better!

Thanks!