I got a really cheap felt fedora cheap on ebay, it's an Australian one for about £25 from UK seller and a replica of Iny one, I just needed to remove the ribbon (unless doing first film) and narrow the brim.
Yup you're correct it was from Chicago's Optimo - it was a brown beaver fedora, the style of the hat wasnt disclosed but besides aging it Mary-An Ceo made some alterations to it as well.