We are 2 couples that are experienced travelers spending several weeks a year in Umbria and Toscana. We are looking for a 1/2 day tour of Siena that concentrates exclusively on the Palio. We know Siena well and visit several times each trip. However, we would like to be lead by a guide who is a member of one of the prominent contrade and can inform us on the customs, events, and history of the Palio. Perhaps, even visit one of the private museums of a contrada. Any suggestions?

We have a list of tour guides on the site. I am not sure if any of them do Siena:

Italy - Trip Planning - Tour Guides

Take a look at Terre di Siena: it is a very nice website with a lot of information.