I googled it and up came several images. But if you type into your search engine "crepe paper party hat 1950s" you will see several for sale - so that should give you some more ideas..
I vaguely recall the type of hat you seek. I don't know a site for them but surely it would not be hard to make a template around a bread/butter size plate from a cereal carton. Then sew a gathered crepe frill around the circumference, followed by a second overlapping frill. I also seem to remember the smaller size had a slit cut from outer edge towards the centre and the two sides overlapped slightly to form a very slight cone hat effect too. Does this help any?
second overlapping frill. Ties were stapled to each side. For a smaller size a slit was cut from outside edge towards the centre and slight overlap at outside edge made it into a slight cone effect. Hope this helps?