While recently perusing the love Duchess of Devonshire blog, I ran across a link for a site selling period straw hats, both men's and women's, called "Just Two Tailors." I was very impressed with their selection, and their fabulous prices - all the basic straw hat forms are around or less than $30! Plus they have Regency era bonnets, in case anybody wants one of those. Here's the link: JUST TWO TAILORS.
They also have a lot of other useful items for 18th c. play, including belts, clasps, panniers, hatpins, patterns, pockets, and more.