The style of Panama hat that you are looking for is known as the "Optimo." As mentioned in this thread, a good quality Panama does not come too cheaply, although less costly versions can be found.
The best place that I know of to purchase the best Panama hats is located on the venerable grounds one of the places frequented by Charlie Chan, the Royal Hawaiian Hotel in Waikiki. It is called Newt at the Royal. You can visit them on the Internet at:
www.newtattheroyal.com
Once at their site, click on the "Optimo" button.
I hope that this has been of some help to you, and good luck in your search.
