Decorating your own bonnet (or retrimming last year's model) was a common past time in Jane Austen's day. This cottage style bonnet, similar in style to many you'll find in Regency fashion plates and portraits, like the included one from Atelier de Modistes Le Bon Genre 28, c.1807. It features a shallow brim (3"  deep on the LG) that fits close to the face and a  22" circumference for the crown. 

This custom plain bonnet was designed specifically for Austentation. It is created from woven synthetic "straw" type braid. It is not straw, but because it is synthetic, it holds up well for packing, playing and all-weather purposes.

I have included some images of sample trimming styles to get your ideas flowing.